Roscoff is an onion town. Seriously. There's plaques up about town how guys used to cross the channel with Roscoff onions - Jhonnies - and sell them to the English; it was the foundation for the town economy for a while. Apparently the Roscoff pink onion was - is - highly regarded. They were smuggling them for a while, anyhow.
Good for a stopover, though. Don't bother with breakfast at the hotels, as is the general rule for France (go to a bakery instead, you'll get much the same or better at a better price.) I stayed in the most seventies hotel in the universe - clean sheets, thankfully, but orange blankets and carpets. It's also the cheapest bed in Roscoff. It looks like there are better places to sleep - and good fish restaurants besides - but I was only in for the night; by eleven o'clock I was at the train station ready to leave.
When all's said and done, Roscoff has a lot of lovely old stone cottages and very little else.