In the frame tab menu on your right hand side, in the tweening section, you will notice an option near the bottom that says 'rotate'. It let's you select the degree of rotation and how many times.
Essentially, you could build the first frame, and then the last frame on 15 (that looks the same), and apply the motion tween for all... in the frame tab, leave everything else without numbers, select 'motion' for tween type, and play with the 'rotation' setting (counter-clockwise, clockwise, etc). This will let you accomplish your rotate without building it yourself. Try this, and if you have issues, post again, and we'll walk through it more specifically. Flash can be wacky with it's animation