Rovigo is a small town and, if you come here as a tourist, you may not need to use the bus. However, if you need to take it, be aware that the service is bad: the most important line (number 1 and 1/, they take you to the train station or the hospital) runs every 30 mins approximately, the other lines, every 40 or 60 mins.
If you want to visit the province of Rovigo (called Polésine), you can use autocars that cover all the territory, although they are not very frequent. All of them leave from the bus station in Piazzale Cervi, opposite to the railway station. This should be a provisional location, since it lies in front of a church and it is not well accessible with urban buses, which run every 30 minutes or more rarely.
You can also reach some interesting destinations by train: Fratta Polésine, Lendinara and Badia Polésine lie on the Rovigo-Verona line, while Adria and Rosolina lie on the Rovigo-Chioggia line. Trains on both lines are old and slow, but quite comfortable and very cheap. They are the ideal means of transport for tourists, but commuters use them quite a lot, as well (especially those to Chioggia).
Train is the most efficient way to reach Rovigo. There are direct connections with Venezia (approximately one every hour), Bologna (the same), Verona (6/7 connections on working days) and Chioggia, on the Adriatic Sea (the same frequence as Verona).
Trains on the Venezia-Bologna line are relatively fast (average speed: 70-80 kms/h) while trains on the Verona-Rovigo and Rovigo-Chioggia are slower (average speed of around 60 kms/h).