What Mark said sounds like the likely culprit. I was having the same problem with my slow rolls when I came back from the season break and it took me a while to pinpoint what was happening. For me it was a combination of getting off the down elevator too early with getting on the rudder too early. For the longest time I had issues with rolling from inverted to upright, it was like a mental block for me, and whenever I lay off the practice for a little while it rears it's ugly head again. I started to fix the issue by flying inverted and then just rolling upright. Once I had worked out all the kinks and felt more comfortable with my timing on it, I incorporated it into the maneuver. I had the toughest time with this on the double immelman in intermediate, and then the bunt w/ 1/2 roll out in Advanced. Keep working at it, at least you know there is a problem, a lot of people have trouble even recognizing that. If you can get your hands on a stick plane (or just carve one yourself), it can make it easier to visualize what might be happening to get you so far off your line.