I think I'd re-balance again to recheck the balance again. Its also possible that your control surfaces are not equal giving you the roll. Try a more dynamic balance check by tying a large loop around the fuselage, then attach the wing setting the loop where it exits the wing saddle on the CG points on each side of the fuselage. Hang the airplane from the loop with a cord a few inches above the floor and see how it balances.

Don't have the Venus 40 should be a great performer just like the Venus II which I'm currently flying.