Greetings, Gianluigi.

Assuming you have made a snare with two piezos you have two choices -
use two inputs on your module or build a DTXpander circuit which will
convert the rim piezo signal into a switch signal. See the files
section for the circuit diagram.

While a Roland is an option, the cheaper Rolands are the same as the
Yamaha - they use a single piezo and rim switch rather than two piezos.

Keith.