"Roasted by fire" (Exodus 12:8) and not roasted on a spit, nor roasted on a grill, nor in an earthenware oven, but rather roasted by fire, that is, roasted from its raw state. You say it means from its raw state, or does it perhaps mean roasted in the manner of something boiled? The verse teaches, "but roasted by fire" (Exodus 12:9). Then what does "roasted by fire" come to teach? That it be roasted from its raw state. "Roasted by fire, and matzot." Scripture has added for it two commandments apart from the commandment stated regarding the offering itself. And which is that one? It is, "You shall not break a bone in it" (Exodus 12:46).
Roasted by Fire Alone and Not on Spit or Grill
Yalkut Shimoni on Torah 197:5
צְלִי אֵשׁ וְלֹא צְלִי שִׁפּוּד וְלֹא צְלִי אַסְּכָּלָא וְלֹא תַּנּוּר שֶׁל חֶרֶס אֶלָּא צְלִי אֵשׁ הַצָּלוּי מִן הַחַי, אַתָּה אוֹמֵר מִן הַחַי, אוֹ אֵינוֹ אֶלָּא הַצָּלוּי כַּמְּבֻשָּׁל, תַּלְמוּד לוֹמַר (להלן פסוק ט) כִּי אִם צְלִי אֵשׁ, הָא מַה תַּלְמוּד לוֹמַר צְלִי אֵשׁ, הַצָּלוּי מִן הַחַי. צְלִי אֵשׁ וּמַצּוֹת. הוֹסִיף לוֹ הַכָּתוּב שְׁתֵּי מִצְוֹת חוּץ מִן הַמִּצְוָה הָאֲמוּרָה בְּגוּפוֹ וְאֵי זֶה, זֶה (להלן פסוק מו) "עֶצֶם לֹא תִשְׁבְּרוּ בּוֹ".