Yesterday, Noisms at Monsters & Manuals asked about information disparity between players and their characters. How much information do you, as GM, give your players? How much do you, as a player, wish to receive?
First off, I rarely give information about rolls for events or details the character can't be aware of, until that information is naturally revealed in context. If there is a 2 in 6 chance that the ogre is in his lair during any given visit, I roll without explaining what the roll is for, other than maybe "I'm rolling to see if something happened." When the roll indicates the ogre is home, that is when they find out.
The exception is when it's a roll a player called for. "Is the ogre looking at the entrance, or is he distracted?" "Are there any human-sized socks in the clothing pile?"
On the other hand, if it's a roll that involves character actions or reactions, I will at least tell them what type of roll it is. "Roll for surprise", but not usually "Roll to see if you were surprised by an ogre." There's got to be a moment of imperfect knowledge, in the case of surprise, but there's always at least some knowledge. If a player wants to shout out an instinctive reaction before finding out what's going on, so much the better. Since I use surprise rolls for more than just ambushes, this is especially important.
The thing to consider is the wandering monster roll. Do you say "I'm rolling for wandering monsters"? Do you say nothing? So you tell them what the possible results are?
I'm OK with players acting on knowledge their characters don't or even can't possibly know. But it's the GM's job to provide some element of surprise. Otherwise, why have a GM?