Most players, are content to use combat spells in combat, but there’s always one or two who want to use their spells more than just in combat. If your Ray of Frost player decides they want to act like Bobby Drake’s Iceman, then you can talk with them about how it isn’t a utility spell. While some people think that the ray of frost is powerful enough to freeze lakes over and add reinforcement to doors, it doesn’t work that way. One of the strategies that some DMs use to illustrate what the spell can and can’t do is to think about liquid nitrogen. If you were to throw a vial of liquid nitrogen at a humanoid, they would get cold and suffer those ill effects. However, if you throw that same vial into a lake, you’d be lucky to get an ice cube out of it all. So, you should talk to your players to let them know while the Ray of Frost might slow down an enemy and freeze them, it isn’t strong enough to do much more unless you cast the spell repeatedly. Even then, that’s a lot of power for not a lot of results.