Yes we noticed that bug. And it happens also if you click on the instrument picture in the Studio. Anyway, you can stop the roll, clicking on the rolling instrument pad without having to disengage the roller effect.
I must admit that because we find a funny use of this issue in Live mode, we have not yet set the high priority to this one
When using Spark without controller, you can trig one roll at a time as you cannot do multiple clicks at once. So let's say you want to use roll for adding some HH at 1/16 on your playing pattern in Live, and make another roll on the snare, you can start the from the techno box your HH roll, and then the snare one and both play together.
Then when you want to stop the HH or snare, just hit the snare or HH pad.
What do you think?
Peharps we should add a preference to enable this mode...