working with a pre loaded snare sample or the E12 snare, you could set the retrigger rate to 64 or 127, and then slowly increase the number of retriggers, while also using an lfo tied to track volume and increasing the lfo amount over time.

Or you could have 2-3 snare tracks… one with the standard and the 2nd/3rd with additional builds, and then possibly add above techniques to taste.

You could also build you pattern in classic mode, then switch to extended when you want to introduce the fill or variated pattern.

External sequencing from your computer another option.

For the OT, besides the retrig & scenes, you could use slices (sample chains) and use a scene to morph through slowly building versions of the pre-recorded roll. Add delay and fast/increasing lfo to vol for gating & extra drilling.