Garda Trentino is easily reached via the daily direct bus service run by Trentino Trasporti from both Rovereto and Trento. Current timetables can be found here.
There are various public bus services to Garda Trentino from Verona, Desenzano, Brescia and Peschiera (A.T.V. buses) and in summer (mid-June to end-September) also from Venice (A.T.V. buses).
In addition, Rovereto and Trento are regularly served by Flixbus. Garda Trentino can be reached in just a few minutes from these two cities on the bus service operated by Trentino Trasporti.