I would be hesitant to use heat.
Is there any apparent movement ? Either fore and aft, or rotational ? If not, it is probably rusted in the frame.
I do not have a ROA, but suspect the mortise for the cylinder pin is bored through the back of the frame. The Blackhawk I have is, as are the Remington clones I have.
First, remove the grip frame, then the hammer. Soak both the front and back ends of the pin liberally with a GOOD penetrating oil for a day or two. Then, use your disassembly instructions to set the pin retainer in the release position. Have someone hold the revolver, or if you have a vice, pad the gun and clamp it in the vise. You should be able to see the back end of the cylinder pin in the hammer mortise in the frame. Use a brass drift, or a steel punch which is slightly smaller than the pin, and try to drive it out from the back. Easy does it, you don't want to peen the end of the pin.
If it doesn't move, soak it with oil, and wait another day, then try driving it out again.