AI have a request to make a 3 tiered cake separated with real roses in between and tier 2 would be rosettes. Tier 1 and 3 would be smooth buttercream with ribbon around the base. I'm concerned how to start by bottom rosette on tier 2 as it will be suspended or separated. Do you have any suggestions in how to make it work? Has anyone done this?

I would think it would be fine just as normal, as the rosettes will stick to the icing underneath.  Otherwise, if you want to be extra sure, why don't you put a slightly larger cake board underneath the second tier, and "rest" the bottom rosette on that (making sure to overlap the edge sufficiently to hide the board).  Am I making sense?

AYes. I 'm guessing I could cut a larger cake board down to get that extra room...certainly rosettes hide a lot! I would love to hear that it has been done before and see pictures of one...can't seem to find one. Thanks for your help.