A cultipacker would be best. It helps firm the seedbed up before planting if you are planting small seeds such as clover or brassicas. It also kind of puts the seeds in rows because of the gulley's created by the disc's, then the water and dirt go into those gulley's when it rains helping the seed out more.
We picked a 6ft pull behind cultipacker up from a scrap yard for $200, if you look around a lot of older farms have them laying around in their junk piles, if you see one, stop in and ask if they will sell it. You might get a great deal on one!
With that being said, a regular lawn roller will work for firming up the seed bed and a piece of fence will work for a drag. We've also used an old bed spring with some weights on it as a drag.
For smaller seeds like clover and brassicas, it is best to roll or cultipack before(for a firm seed bed, you don't want it going more than 1/4" in the ground) and after (for good seed/soil contact).
For bigger seed such as soybeans and corn its best to work up the ground, spread your fertilizer and seed, then work the seed in with your disk(harrows straightened) then roll it or cultipack it.
Don't get me wrong, if you scratch up some dirt and through out some brassicas, stuff will grow and you might be happy.
I'm just saying what would be best so you have an idea and know your options.
We've planted a field of soybeans with nothing more than a bed spring,4 wheeler, spreader, and a burrowed roller.
Genesis 27:3 Take your bow and quiver full of arrows out into the open country, and hunt some wild game.....