Not at all, just ask anything
Rovinj is pretty crowdy in July and August, unfortunately. But it's not unbearable (like in Dubrovnik for example where you have to walk in the river of people through the streets)
If you really don't like crowds than maybe it would be best to avoid July and August. I personally would choose late September to visit Rovinj because the weather is still warm and sunny but it's not that crowdy anymore.