Many roads lead to Rovinj and we'll help you find the best one for you with some personal recommendations.
We recommend you check out some more detailed resource of arrival to Rovinj from tourist board of Rovinj.
Although Rovinj has no airport there are several airports you can choose from while checking the flight connections. For more information make sure you follow this link (coming to Rovinj by plane)
There are some cheap airlines (EasyJet, Flyglobespan, German Wings, Ryan Air, ScandJet, TUIFly, Wizzair) flying to these town. There is a great page that might help you find the right flight for you!
For all salseros coming from Italy or passing through Italy, you might want to look at a ferry line from Venice to Rovinj. Please look at this link for more information:
Coming by car? Having your own transportation? Look at some of the rout planning sites:
The closest train stations are in Rijeka and Pula. You can take the bus from there to Rovinj.
For some general regulations in Croatia, please look at the following pages:
Also, a site of Croatian Tourist Board can help you find some more info on travel to Croatia.