Many years ago multiple nail holes were filled and the walls painted with two coats of semi-gloss paint. The patched areas were not primed. The patches show as 2-3 inch round flat areas that do not have the roller texture. We are now preparing to repaint the room. How can we fix the flat areas that show?
You need to add the roller texture to the patched areas. To do this all you need is some drywall joint compound (all purpose) and some acrylic primer. Mix some drywall compound into some primer. The mix shouldn't be thick, just enough compound to give a texture. Now use a small roller, 3-4 inch and apply this mixture to the patched areas. After it dries you can touch-up the newly textured areas.
You could just use the drywall compound mixed with water but the patched areas will need some primer first. Also, the compound by itself is hard to roll.