what kind of rose is it? some roses just have thin stems.

Crystal, I believe sometimes it is exposure, The canes on my roses on thinner than a rose gardener's down the street. She has a lot more daylight and sunlight and her stems are thicker and bushers are shorter. Mine, with a lot of tall dense trees around, seem to grow taller with narrower canes - I believe reaching for more light. I probably get the same amount of blooms as she does though. Anyway, just a thought, if you have similar condition as me then that could be the reason.
Pauline - Vancouver Island

If the roses are modern (HTs and Floribundas) and if they're less than four years old, you may have been fertilizing to grow blooms rather than to grow the roots and stems.
If you want bigger stems (and healthier roots) you might want to look at some of the organic soil amendments. And(you can't do it this year) you do this by adding some thing like Mills Magic Mix (or equivalent) in early spring and make sure to water the roses really well. Mills MM is a combo of things like alfalfa, cottonseed meal, soybean meal, some epsom salts, minors of bone meal, blood meal, compost, and they also use Millorganite in the mix. A lot of us mix our own (my version leaves out the Millorganite and adds gypsum.
I had the same problem as to O.P., but I changed the way my roses grow by deciding to grow better plants. Better blooms came also without my worrying about the blooms.

Ann, thanks for this. Mine (on the whole) have been terrifyingly tall this year. Way taller than me, I do not like that. I do use Epsom Salts (and Alphalfa this year for the first time) but not in a tea. I have too many roses for that. We also use our own compost and usually a commercial rose food. I do not think we have Mills Magic Mix here. You say you make your own. So would you please mind telling me what you would add to the alphalfa and Epsom salts and what numbers should I be looking for in the commercial feed. Greatly appreciated.
Pauline - Vancouver Island