What exercises should I start with after a rotator cuff injury?

If you're doing better and you can start moving around a little bit, you could start doing isometric shoulder exercises. For example, stand next to a wall, pinch your shoulder blade back, and push the side of your elbow into the wall gently, holding it for 5 seconds. Repeat 7-10 times. You can also try standing, bending your elbow at 90 degrees, making a fist, and then pushing that into a wall. Or, you can push your elbow backward if you're standing with your back against the wall. Those are the three most basic exercises that I would start off with. They should be pain-free.