Maybe a little spinner or spoon would work. Don't reel in fast, just fast enough to not snag it on the bottom. If you are allowed bait, then a garden worm on a small hook under a float would probably be effective. If you fly fish, then a small gold-bead head hares' ear nymph is pretty much one of the best river trout patterns tied and represents lots of stuff that lives in the stream.
Probably more important that deciding which lure/bait to use is knowing where teh fish are in the river. In cold weather, their metabolism is slow and they'll be in deeper, slower-moving water, as it warms up their metabolism increases and insect life in the stream "wakes up" in the riffles. Trout will sit where fast shallow water over a gravel bottom enters a deeper section of river as there will be food and oxygen present.