I'm having trouble getting a good single-note one-handed roll. I was wondering if anyone had any suggestions. I play traditional grip. Thank you.

Hi,
I would say just work on it slowly until you build it up, there is no short cuts that I have found. I play traditional grip also, and I found that I had to experiment with the height of my marimba to get a good roll. Incedently, it actually taught me where the best height was for my marimba. Though it is different from one person to another, I would say that you would probably want the height audjust a little higher than that of what a Stevens grip user would do, as Stevens players seem to have more of a break at their wrist, and with traditional (especially with one handed rolls) I find that a straighter wrist is more benefitial. I must stress though that this is just MY way of doing it. Though it might not be the solution for you, it is worth looking into. Good luck!
~Behzad