Pac has a fairly well-rounded matchup against almost the entire roster just because of his sheer versatility. Against a Villager, I don't change up my play at all, just because Villager has a tough time getting stage control as fast as Pac does. Fruits for harassment (don't be afraid of pockets, it means they can't use invincibility tech with it anymore until they ditch the fruit), Hydrants for bait and mixups, and trampolines because Villager's aerials limit his/her options for ground control. As long as you play more defensively than your opponent, Villager isn't too much of a threat. Remember to take into account that Villager has a lot of options like Pac. If Villager pockets Hydrant, Pac still has a huge advantage, because Villager can only launch the Hydrant from pocket if he/she caught one that was already launched. Because of this, figure out whether your opponent is pocket happy, and then, if so, approach from the air and drop a Hydrant in front of him/her. They'll pocket it, and you'll have, essentially, safe fruit play for 30 seconds or until they ditch it. Remember that Hydrant is almost always more effective for baiting than anything else. People see something that they can use against their opponent, and suddenly, they've developed tunnel vision.
R.O.B. is a different story, but he is less of a problem. R.O.B.'s aerial combos are based on u-air and f-air, so, like Nimbus said, do crossups on the ground to get behind him and use RAR f-airs on landings (don't frequent them, though, the opponent can catch on), cherries on gyros and off-stage to gimp, and try to refrain from launching hydrant too much. R.O.B.'s reflector can be angled to cover just about every launching Hydrant option Pac has. Instead, try dropping one on the ground and using PP into the floor to go into your downed state. Let the water push you under R.O.B.'s lasers and gyros so you can approach with rolls, get ups, and get up attacks. This is a great mixup approach that works on lots of characters that don't have too much low ground coverage, and R.O.B. is so tall that the only definite way you can be punished for this is if he reacts with d-smash and clanks, but even then, an uncharged d-smash will not stun Pac long enough for R.O.B. to get any serious punishment off. A d-tilt could catch you if your opponent reacts fast enough, but keep in mind that Pac is all about mixups. Use everything in different ways each match and you'll do just fine.