The rootstock, if any, WILL bloom - it will just be a different rose, probably an old once bloomer of some kind. What I would do is let all of the roses bloom, so that you can see what they are.

Jackie

The common rootstock varieties will not bloom on canes that are new this year-- only on canes that have been through winter. They are once-blooming or June-blooming varieties. New canes (of repeat-blooming roses) that started in April will bloom soon, while canes of once-bloomers will just keep growing through the summer. You may have some plants with a mixture of rootstock canes and scion (grafted, repeating variety) canes. These will have different leaves and maybe different thorns. Locate the graft, and remove the canes coming from below it. You need to rip these out at the point of origin, and not just cut them back.

I'm guessing you are in the PNW or your roses would be in full bloom by now.