Recently I made guest favors for a wedding shower. We have a red rose bush in bloom which had lots of flowers, but none of them had long stems.
To make it a little extra classy, I put polished river rocks (the sort of thing you would find to fill vases/glass lamps/etc at pottery barn) at the bottom of the vases. I had considered glass jewels or the like, but decided it would be too ostentatious.
I also got another candle holder so I could try floating a rose. It worked
out pretty well.
To make the blooms last longer, cut the flowers in the morning and at an angle
All Cut Flower ideas here.