I highly recommend Peters place!
I spent there almost 3 month and it was perfect. The place is great and offers everything you need. Its clean, comfortable and cozy.
The location of the place is great as well. It is very central. You just walk 10 minutes to the markthal and Bars and supermarkets are around the corner and still it is in a quiet area. And you reach the University very easliy with the tram (just 3 stations).
And most important. Peter is a great host. He is responsible and assure that your stay in Rotterdam is best as possible.