I have used both the last few years. the right answer may depend on what you used to seed your timothy/alfalfa. if you used a seeder that you feel confident that the seed was planted below the surface of the ground, a roller would be OK in most cases. if you had it custom applied and just deposited on top of the ground, the cultipacker would have to be used. seed that remains on top of the soil will only have about a 20% chance to germinate and grow even after pressed down with the roller. In my case, my old seeder has disc openers for larger seed like oats but the alfalfa seed just drops on the surface of the ground, so the cultipacker works best for me. the cultipacker will also help level the ground which the roller does not do a very good job doing. I prefer the cultipacker with the teeth set so they just scratch the surface to about an inch down. I use the cultipacker before and after seeding but the before seeding pass has the teeth down deeper to get a softer seed bed.