Question: I had my first session as Dungeon Master (DM) yesterday playing pathfinder ("First Steps In Lore" from the "Pathfinder Society" series) with a group of first-time tabletop RPG players (myself included). Overall the sessions went well, a good crash course for everyone and everyone seemed to enjoy themselves.

My question is a problem I personally had while DMing. I taught the players that they can roll for perception to check things out, finding traps and secrets, etc. The players got the idea and started saying "roll for perspection to check out the room", etc., and they found a couple of traps that way, and that's fine. The problem I had was: What do I do with all the "useless" rolls?

Most of the time they were rolling when there was nothing to find. Even on a natural 20 I kind of just described the room in more detail while saying something like "but there is nothing of interest".

Is there a better way of approaching this? Do I make something up?

I'd like to add: I would prefer my players roll their perception checks when they are actively looking. I am not a fan of the hidden-DM-rolls-for-all-perception idea.

Answer: 
We assume that players are by default going around being perceptive at an ordinary level. If there's an interesting detail that might escape the players' notice, the DM will call for the relevant characters (maybe everyone, maybe the guy in front, maybe the characters with darkvision, etc...) to make a perception check. If everyone who was given the opportunity fails it, there's no opportunity for anyone else to metagame and make the check. The downside is, if everyone rolls a low number and the DM says "ok, you don't notice anything interesting" then the players know that they have missed something. Sometimes there are immediate consequences (the orcs jump out from behind the bushes and surprise you, you fall into the pit trap you failed to notice, etc...) but other times not, and you're left wondering if you missed something important.

A partial antidote to that is to sometimes tell them they found something, but it's not the thing that you were offering the perception check for. If they were close, maybe they get a hint as to what they failed to perceive. Otherwise they "perceive" something totally different, and unimportant. You can also sometimes offer a perception check to find some small detail that isn't plot relevant, like "You notice some initials carved in that tree over there." This has the advantage of not "giving away" that something is significant, just because the players rolled a high perception check and found something. (If you're going to play this way, you should warn your players that not everything they perceive is going to be important to the plot, or they may waste too much time on red herrings.)

To answer the question of what to do when players want to examine something, and roll high, but there's nothing to find, you can occasionally also insert irrelevant details. You notice that the second drawer of the dresser sticks when you try to open it. You notice scuff marks on the floor near the window. And so on. So yes, I would sometimes "make stuff up". I think it's fine to also say, "nothing appears exceptional or unusual in this room" a fair amount of the time.
Perception rolls, like Stealth rolls, should be rolled by the GM out of sight of the players. The players should not know if they rolled high or low, just what they find.