Albert Barnes Commentary Isaiah 44:16

"He burneth part thereof in the fire; with part thereof he eateth flesh; he roasteth roast, and is satisfied; yea, he warmeth himself, and saith, Aha, I am warm, I have seen the fire." — Isaiah 44:16 (ASV)

With part thereof he eateth flesh — That is, he prepares flesh to eat, or prepares his food.

He roasteth roast — He roasts meat.