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: 
So, what's the downside of saying, "nope, you find nothing"?

You're committed to letting players make their own rolls (which is perfectly fine, though not everyone plays that way), so they already know that they hit a DC of 23 or less (or whatever). There is no need to punish yourself or them by pretending otherwise.

It's not even particularly bad in terms of meta-gaming, if you are willing to decide that characters have some sense of how effective their perception rolls have been. If you don't like that, then by letting the players roll they are taking responsibility for not using knowledge of the die roll to meta-game. (This is often why people advocate having the GM do perception rolls in secret).

I've had some success as a GM by using the "PCs search an empty room" situation to advantage to add some realism and depth of involvement, by having things that aren't really important but which fit the location, or that I think are cool. So things like utensils that fell behind something, a damaged straw doll, a broken weapon, dice, pottery. (Yes, you do run the risk of a player spending an hour on "the mystery of the rusty spoon"). 

That also helps a bit with the "the GM mentioned it so it must be part of the plot" meta-gaming.

Ultimately, if you have something that contributes to your game when there is a perception check, use it. If you don't, move on fast to get to things that do.
have the players roll a bunch of perception rolls at the beginning, list them all and cross them off as you go, they know the rolled them, but have no idea if they see nothing because of a bad roll, or if there is truely nothing to see.