Question
Hi Ken! We live in WI, zone 4, near Madison. When we moved in here 12 yrs ago, the ground was land-fill,broken glass, nails, real bad dirt. We got 128 yds pasture and spread and seeded it. We didn't think to roll it at the time.Now the lawn is like walking on bumps every where, and it hurts your feet. My husband wants to get more dirt, till it into the lawn, smooth, roll, and seed it. I want to get more dirt,spread it on the exsisting lawn,roll and seed it.We are wondering if you can help us decide what to do. We want a nice smooth lawn to walk on. Thanks!  

Answer
Either way will work. You can till it which will give best consistency, but it leaves no original grass left. If you do not till, you will likely keep some of the original grass, but you risk that it will not be as even as with tilling. The choice is yours. I would probably go for tilling the soil since you already seems determined on reseeding.

After seeding, roll again to ensure good soil/seed contact. Then keep seedbed consistently moist until germination.

Good luck