It is really easy to reach Riva del Garda..
From the hihgway Brennero - Verona (Autostrada A22): Take the exit Rovereto sud, direction: Lago di Garda - Riva del Garda.
There are many different ways to reach Riva: organized buses, renting car, ecc.
Please, read the document below, it contains detailed informations about thansports.
Detailed informations:: Transport