m_skaggs,

Are you giving it a shot of down elevator (up stick) when the plane hits the inverted portion of the roll? I used to have the same problem, until someone told me of this. When flying inverted, the plane is going to try going nose down unless you give it down elevator to push the nose back toward the sky. In a roll, you just have to do it for the brief moment that the plane is inverted. (And to really do the roll correctly, you'd give left and right elevator to keep the nose level when the plane is on its side, too.)

--
Tom