That water filled roller thingy for making a new lawn is critical. I would get out there and roll your lawn's soil bed. Now. Oh well if you screw up a few seeds. Before rolling spread a thin layer of more seed, then roll. Horizontally, vertically, diagonally...this is the only way to ensure a beautiful lawn.
It takes 11 days of germination before one should mow the lawn with a lawn mower, very very sharp blades, bag those clippings please (use in your compost pile or on weeds). We are talking about cool season grasses, yes?
Watering shallowly every day sometimes up to 10 X per day in hot weather. You have to keep the seed bed moist or all the germinated grasses will die when the seed bed dries out. This is the only time in your lawn's life it should be watered shallowly and often!
If we are talking about cool season grasses make DANG sure your mower deck is raised to it's highest setting. I had mowers fitted with manual lifts...3 1/2 inches is perfect. 3" is bare minimum height to leave your grass after cutting. That top growth is so very necessary to grow and encourage and train the roots of your grass crop! Cool season grasses have HUGE root systems, genetically. Water deeply ( at least 4") use a shovel to slice into your lawn to observe 4" Make note of the time it took to water with whatever sprinkler you are going to be using to get moisture 4 to 6" deep.
After watering deeply do not water again until you see your foot prints on the grass. When the blades of grass aren't turgid enough to stand back up after being stepped upon, THAT is the time to water deeply again. You are training your grass to grow deep and when a drought hits? your grass will not go dormant. You will have green grass and very minimized water bills.
Aerate once per year taking out plugs of grass and soil and leaving those plugs where they fall. Rent this machine and get your neighbors on board so they can do their lawns once per year.
Fertilize 4X per year. Use the correct formula for the time of year.
While your baby grass is growing do not fertilize. Fertilize after the first mow. I suggest Dr.Earth's Lawn Fertilizer, not Scotts or Ortho...you will only need to fertilize 3 times per year. Slower to green but my goodness, I made lawns and maintained lawns for the rich and famous...Slow release fertilizer is best for your grass plants.
Blow off the excess fertilizer from your concrete walkways, curbs and drive way. You gotta have a gas powered blower along with your hydrostatic mower with extra sharpened blades and the deck RAISED up so you cut no shorter than 3 inches. 3 1/2" is far better. You gotta have a gas powered line trimmer for all the edges and lots of other things, Stihl is my favorite still, ha ha, after 30 years. There is an art to line trimmers, weed wackers? Wear safety glasses, ear protection. Be aware of your surroundings..
Seeding a lawn by hand is not a great way to start a lawn. I'd rather you use a seed spray company or truly the best way to start a lawn is using SOD. Most lawns that are seeded by the owner are replaced in 3 years. By someone like me.
Alephzero has a solution, wait until that grass needs mowing before you roll it with a weighted roller. Or you can do it now, do a second seeding first then roll!
For the few lawns I had to seed, I seeded once every week for 3 weeks. That roller will cause better soil, seed, root contact.
Use a seed spreader. Use a fertilizer spreader (usually the same piece of very inexpensive equipment). A rotary hand spreader, cheap cheap cheap but ... Never throw seed or fertilizer by hand, never.
Getting your seed bed firmly compacted and graded is the basis of a good lawn. Without rolling, a lawn will look like well, a home owner did it.
Spread more seed before rolling. The rolling settles the seed into the soil. Do not fertilize until your lawn is thick and full. 2 weeks of growth? Right after the first mowing. Seeds actually have the chemistry and calories baby plants need in the beginning. Too much and you will weaken your grass crop. This is all about baby grasses, not a mature lawn.
Seeding a new lawn always takes at least 2 seedings. If you crush a few germinated seeds by rolling, big deal. That rolling is as important as the quality of seed you've purchased.
If this doesn't work for you, please check out using sod. It truly is not a big price difference! Using sod one can do a DIY. Is not that tough. Using sod solves one heck of a lot of problems. Don't mow until you are unable to pull up the sod. Make sure it has rooted. A rotary mower will suck up the sod just like a carpet.
Sounds like you did everything correctly except one of the most important things to make a lawn...rolling.
If you have warm season grasses...there are very different management and planting practices! I am just so very glad you were thinking about the rolling!! Very rare for homeowners to understand.