I'm a newbie, about 4 years now I've been a newbie.
I went to a basics class the other night. Lots of new people were there and the instructor started with ukemi drills. This one was interesting.
Sit in seiza, and reach between your legs with the arm you intend to roll on as far as you can. As you reach further your hand ends up back by your feet (or past), and your shoulder touches the mat. Keep reaching and start to push off with the foot opposite of the arm you're rolling on. Push just enough to tip yourself over the balance point. Y'all are probably past this type of excercise, but I found it very interesting to get the 'feel' of how the roll should, uh...feel.
As I've progressed, I find the unbendable arm thingy is very important for forward rolls. If it collapses, your shoulder is next in line. Pointing your elbow in the direction of the roll, and your finger tips back at you, introduces tension into the arm. This allows it to be "springy"
Take your time, you'll get it.