That is very unfortunate. You don't say how many weeks ago you sowed the seed,but if the seedlings are only as tall as you say, I'm assuming it was pretty recent. I think you will have to risk going in to try to repair the damage by smoothing out dented areas, even if that means further damage to seedlings. Use a board or two of some sort to walk on and stand on that you can work off to spread the weight of your body to reduce further damage (I keep old wooden shelving for this purpose). You may need to fill in divots with extra topsoil and definitely more seed - spread out clumps, again even if it means damaging seedlings in the clump further, and add more seed if necessary. And make sure the dog is not able to get in there again, obviously....
It's better to do it now, especially for the clumped up areas, to avoid ending up with small hillocks of thick grass later on. Keep it well watered as necessary, and cut it when it gets to about 6 inches, preferably with shears or a hover mower so as not to rip out the seedlings by the root for the first cut. This cutting is necessary not just to reduce height, but to encourage tillering to thicken up the grass spread. I don't know where you are in the world, but in the UK, a roller has no role to play when creating a lawn and is not recommended, other than to press down recently laid turf which may have lifted due to frost.