I only just began introducing my males & females together this weekend, mostly b/c winter has lingered on here longer than the rest of the country.
So far, my bajas and 'snow project' rosies have been the only ones going at it; the others have not been interested. It's easy to get worried from the get go, but mating season lasts a long time. Once your female starts emitting pheromones, your male won't be able to resist!
Hopefully(for you) he won't shoot blanks. That's my big fear. Even though she may be obviously gravid, she may only drop slugs. That happened to two of my females last year. Both mated with the same male who avidly bred with them.
Just keep on introducing him every few days. For a male I'm only mating with one female, I use a 5 days on 2 days off method.
I keep this up (usually)from early April thru late June.
Good luck & keep us informed.