I have the same problem, airrick. The first knuckle on my pinkie bends back a bit and sometimes "locks" so that it stays straight. I especially have troble "rolling" from the second degree of a major scale to the fifth degree of a major scale. I think that the best thing to do is focus on using as much of your finger-tip as possible, so that you don't have to "roll" as much. Also, work with a metronome at a very slow pace. I mean 60 BPM and even slower. Gary Willis, on his website
www.garywillis.com, suggests going as slow as 30 BPM!
Good luck, bro. Let us know how it goes.