Gemara

(Beraisa): If one cooked the Pesach and then roasted it, or vice-versa [and ate it], he is liable.

Question: Granted, if he cooked it and then roasted it he is liable, for it was cooked;

However, if he roasted it and then cooked it, it is "Tzeli Esh" (roasted). Why is he liable?!

Answer #1 (Rav Kahana): The Beraisa is R. Yosi:

(Beraisa - R. Meir): One is Yotzei Matzah with a wafer that was cooked but did not dissolve;

R. Yosi disagrees.

Answer #2 (Ula): It is even like R. Meir. "U'Vashel Mevushal" forbids if it was cooked at any time.

Berachos 38b (Rav Chisda citing Rav): One blesses Borei Pri ha'Adamah on Shelakos (cooked vegetables).

(Ula citing R. Yochanan): One blesses sheha'Kol.

(Rav Chisda): [All agree that] we say Borei Pri ha'Adamah on Shelakos only if we say sheha'Kol [when they are raw, for they are normally cooked].

(Rav Nachman): Shmuel says Borei Pri ha'Adamah. He and R. Yochanan argue like R. Meir and R. Yosi [above].

Rejection: No, all say Borei Pri ha'Adamah on Shelakos;

R. Yosi disqualifies cooked Matzah because it loses the taste of Matzah. He agrees that vegetables do not lose their Berachah.

(R. Chiya bar Aba citing R. Yochanan): One blesses Borei Pri ha'Adamah on Shelakos.

(Rav Nachman bar Yitzchak and R. Zeira): This is truly R. Yochanan's opinion. He blesses Borei Pri ha'Adamah on a bean cooked in a pot.

Rishonim

Tosfos (41a DH Ula): Ula equates Pesach to cooking Matzah, unlike the conclusion in Berachos 38b. There, Ula says that R. Yochanan says sheha'Kol on Shelakos according to R. Yosi. We rejected this. R. Yosi discusses only Matzah. Also here, Ula holds, unlike the rejection, that R. Yosi holds that Bishul is Mevatel [roasting or baking].

Tosfos (41a DH Aval): Rashi explains that Bishul is Mevatel the law of bread. He holds that we discuss a soft kneading. If it is a thick kneading, it does not lose the law of bread. The Ri holds that we discuss a thick kneading. It is Pasul because it is Matzah Ashirah. Just like R. Yosi holds that through Bishul it loses the law of baked, to make it Matzah Ashirah, as if it was not baked, also regarding Pesach, Bishul makes it lose the status of roasted.

Poskim

Shulchan Aruch (OC 318:5): Some say that something that was baked or roasted, if it was cooked afterwards in liquid, Bishul applies, so one may not put bread even in a Kli Sheni that is Yad Soledes Bo.

Beis Yosef (DH v'Chasav, citing Semag): There is not Bishul Acher Bishul, like the Mishnah (Shabbos 145b) says "anything that was in hot water [before Shabbos, one may soak it in hot water on Shabbos]. Re'em explains that it was fully cooked in a Kli Rishon. However, there is Bishul Acher roasting or baking. We hold like R. Yosi, who says that one is not Yotzei with a wafer cooked after it was baked. Bishul is Mevatel the baking. Therefore, one may not put baked bread even in a Kli Sheni on Shabbos in a place that is Yad Soledes Bo. One must be careful also about roasting. If meat or fish was cooked, one may not put it near a fire where it is Yad Soledes Bo. If he did, he was Mechalel Shabbos. Perhaps he is Chayav Skilah [if he was Mezid] or Chatas [if he was Shogeg]. It seems that the Re'em is stringent even for a Kli Sheni.

Beis Yosef (ibid.): It seems that he holds that some things get cooked even in a Kli Sheni, like we say (Shabbos 42b) that salt gets cooked even in a Kli Sheni.

Taz (7): The Tur holds that the only cooking we find in a Kli Sheni is salt.

Magen Avraham (17): Likewise, there is roasting after Bishul. One may not put something cooked near a fire without liquid.

Mishnah Berurah (41): One may not return cooked meat to an oven without liquid, even on top of a pot on the oven. Bishul after roasting applies even if it is still hot from roasting.

Bi'ur Halachah (DH Yesh): The Pri Megadim says that roasting after Bishul is not Mevatel the Bishul, so if meat was cooked and roasted, one may soak it in hot water. Presumably, he holds that Bishul after roasting is not Mevatel the roasting, for Re'em equates them. I disagree. Even though it does not lose the first name, it also gets the latter name, so now he does Bishul after roasting. I say that the latter name is primary, so if he cooked and then roasted before Shabbos, he may roast it on Shabbos.

Note: The Gemara held that it is obvious that one is liable for Pesach cooked and then roasted, i.e. the first action is primary!

Me'or ha'Shabbos (12:52, cited in note 331 in Oz v'Hadar Mishnah Berurah): According to the Bi'ur Halachah, why may one put instant coffee in a Kli Rishon? It was cooked, and then dried in a hot oven! Ha'Gaon R. S. Z. Auerbach, Ztz"l said "the Mishnah Berurah's stringency is difficult. Iglei Tal and Shevisas ha'Shabbos disagree. Perhaps the Mishnah Berurah discusses only when it became soft through Bishul, so the change is felt. Coffee dissolves, so the change is not felt."

Kaf ha'Chayim (78): In a pot, even without liquid, is cooking. One may not put baked bread near a fire, for it gets a different taste (roasted).

Kaf ha'Chayim (65): Most permit putting roasted ground coffee into hot water. Ben Ish Chai says to mix it with water before Shabbos, and add it to a Kli Sheni on Shabbos, to avoid coloring on Shabbos.

Shulchan Aruch (ibid.): Some permit.

Beis Yosef (DH veha'Mordechai): The Mordechai brought Re'em's proof, and said that Avi ha'Ezri disagreed, for in Berachos we concluded that R. Yosi discusses only Matzah, which must have the taste of Matzah. Tosfos (DH Aval) says that even for Matzah, Bishul does not uproot the status of baked. Avi ha'Ezri's question is strong. In Berachos we conclude that all agree that one blesses Borei Peri ha'Adamah on Shelakos. R. Yosi argues only about Matzah, for it loses its taste. Here, even R. Yosi agrees. All the Poskim say to bless Borei Peri ha'Adamah on Shelakos, and we hold like R. Yosi. It must be because Matzah loses its taste.

Beis Yosef (DH u'Semak): Also Semak wrote like Re'em. He proved that there is Bishul after roasting from 41a. All agree that there is no roasting after roasting, or baking after baking. Re'em forbids Bishul in water after baking or roasting, like the cooked wafer. Some say that he forbids even roasting after roasting. This is wrong. His proof from Pesach is only if he later cooked it in water or wine. Just like Avi ha'Ezri proved from Berachos that Bishul is not Mevatel baking, and Matzah is different, we can say that liability for eating Pesach that was roasted and then cooked is not because cooking is Mevatel roasting, rather, due to "Bashel Mevushal."

Taz (6): I answer for Re'em that he holds like R. Yerucham and R. Yonah (Sa'if 4) that after it was fully cooked, Bishul does not apply to Mitztamek v'Ra Lo (he is displeased that it dries out through additional cooking). Bishul applies to Mitztamek v'Yafah Lo, for he benefits from a new taste that came through Melachah on Shabbos. Here, even if we say that R. Yosi disqualifies because cooked Matzah has a different taste, this does not apply to Pesach, which must be roasted. It does not depend on taste. We can say that it is still considered roasted. Regarding Shabbos, if the taste changed, we can say that he intended for this. It is no worse than Mitztamek v'Yafeh Lo, to which Bishul applies even after Bishul, and all the more so after baking. This is according to Tosfos, who holds that we can distinguish Matzah, which requires the taste of Matzah, from Pesach. We must say that "we require the taste of roasted meat" does not apply. There is a special Limud about Matzah, i.e. Lechem Oni. The Re'em holds that similarly, we require the taste of roasted meat. Regarding Berachah, the rejection is valid. The same taste remains after cooking. It improved! It should not lose the Berachah. Regarding Shabbos, we cannot reject this. The Torah forbids intended Melachah. All the more so it is forbidden mid'Rabanan due to the changed taste.

Magen Avraham (19): I brought (15) from Tosfos (Shabbos 39a DH Kol) that one should be stringent, for it looks like cooking. The lenient opinion holds like Tosfos' other answer. The Shulchan Aruch is lenient. One should be stringent.

Gra (DH v'Yesh): This opinion is like Tosfos (DH Ula).

Kaf ha'Chayim (84): The Mechaber favors the lenient opinion, for he brought it last.

Rema: They (the latter opinion) permit in a Kli Sheni. Some permit even in a Kli Rishon.

Magen Avraham (20): Since it is dry, there is no Bishul after baking.

Rema (ibid.): The custom is to be careful l'Chatchilah not to put bread even in a Kli Sheni as long as it is Yad Soledes Bo.

Beis Yosef (ibid.): Hagahos Maimoniyos says that Re'em did not forbid putting bread in a Kli Sheni according to letter of the law. There are two versions about salt. One version says that it is not cooked even in a Kli Rishon. The latter says that it is cooked even in a Kli Sheni. The former is primary, just it is good to be stringent like the latter. In any case, this shows that some things get cooked in a Kli Sheni. We are not experts about what is easily cooked. Therefore, one must be careful about bread.

Beis Yosef (ibid.): This answers the Tur's astonishment why he forbids in a Kli Sheni. For salt, we hold like the first version. Also Re'em agrees. Even so, some things get cooked in a Kli Sheni, and we are not experts, so one must be careful.

Mishnah Berurah (45,47): All the more so, one may not pour from a Kli Rishon [onto bread]. One may put bread into a Kli Shelishi, or into a Kli less than Yad Soledes Bo.

Mishnah Berurah (46): B'Di'eved, one may rely on the lenient opinion, even if he put it in a Kli Rishon.

Mishnah Berurah (48): The Chayei Adam says that if it is Yad Nichbis Bo (hot enough to scald a hand), all agree that even a Kli Sheni cooks.

Kaf ha'Chayim (86): Many Poskim permit putting bread in a Kli Sheni. One who is stringent will be blessed.