In this tutorial, you can see how to use a simple technique to create a roll effect with a sample.
The idea is to get a percussion sample such as a cowbell, a snare, etc. (the longer the tail of the sample the better for this technique), in the AudioFile Processor, set the "Enable Loop" icon ON and then automate the "Sample End" to your liking. Put a long note on the piano roll and that's all!
You can automate the Pan or the Volume (in my case via an amplifier in the FX section) to give it more movement.
Additionally, you can use different FX to change the sound. In my case, I used a little bit of distorsion, saturation and reverb.
This technique can also be used to create basic riser effects, following the same idea (listen to the end).