I'm hoping to do a whole garland of roses, so I pre-cut a LOT of things while watching a movie one night...
Instead of hot gluing while I go, I just roll the whole thing up and make sure I like how it looks
(which I do)
I then insert a needle with knotted thread in to the very center, and aim for one side
Pull the needle and thread through, then make a quick loop back towards the center
Then come back out the middle and do it all over again to another side of the rose
Then, when you're comfortable with the number of stitches (I've been doing four and it works out well), just come back to the center and make a little knot in the middle!
I've always had a bit of bad luck with hot glue, but a needle and thread are my best friend! Since these will have something on the backs, the knots won't be visible or matter, and the same will hold true if you're doing hair pins like Little Things Bring Smiles showed you how to do. Of course, hot glue will probably be best if you're attaching it to something like a headband, but the sewing trick works great and I think is just as quick and easier to do if you're not going to be in one place for a while. I do my crafting at home, on the road, and in the office when I have spare time (during pickup I can't start any work projects, but I can usually get a flower sewn up pretty quickly) and a hot glue gun isn't exactly portable!
I promise I'll share the garland when it's finished, but since I have until spring (it's for a friend's wedding) it may be a few weeks!