How fun, Joe! Yes, you can either transplant them or leave them where they are, depending upon what fits better with your space and how you want the roses laid out. Yes, it is common for seedlings to spring up from seed which fall on the ground. That's how it often works in Nature. Several really neat roses have arisen that way at The San Jose Heritage Rose Garden and you'd be surprised how many commercial roses, particularly OGRs came about that way. You know how to transplant and pot roses, so you don't need any advice for that. It should be interesting watching them to see how closely they resemble Bonica or if they are significantly different. You'll have fun with them. Congratulations! Kim