Yes, you can do as "sluk" suggests. And yes, tilling/rolling/levelling can possibly create an uneven turf.
If you're committed to sod - many folks are in spite of the half price of simply overseeding - then you can forget about tilling...you won't go to hell.
This, of course, is dependent on whether or not you have construction grade hard-as-a-rock surface adobe clay.
Level it out w/loam (topsoil), water and roll the spots, spread a thin layer of chicken manure/redwood compost mix or a mushroom compost mix, lay down starter fert, proceed w/the sod, then another slight top layer of starter fert. Once the sod roots get purchase you can aerate it with a commercial grade aerator - not those silly drums w/spikes that Jose Gomez rents and "aerates" your lawn for cheap...they will just skip over the surface. Commercial grade aerators, like my Ryan LA-28 (its For Sale), have 3/4" + diameter spikes mounted on a crank shaft that will vertically drive down creating ~4" - 5" long plugs. Aerating will open (decompact) the soil and allow the roots to flourish. Allow the plugs to remain and decompose - good nutrients in them. Then later, if you're inclined, you can spread another thin layer of the above-suggested composts onto the new sod to renovate (decompact) the soil even more.
Or, just have it overseeded using a commercial grade machine like my Ryan Mataway/Overseeder.
I've done it both ways w/great success. In the past, I would talk discriminating clients out of tilling/laying sod and would suggest overseeding instead. Not immediate lawn like sod, but after the first few mowings they were pleased w/the professional job and the big $$$$$ savings.
I dislike laying sod, BTW. Too labor-intensive > costly.
My suggestion, if your soil is not compacted adobe clay and reasonably flat, spot-level it and go w/overseeding.
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Here's my Ryan Mataway/Overseeder.
This is the E-ticket for overseeding/de-thatching/renovating turf.
One bad-ass mosheen (and it's For Sale, $3k, mint - come get it).
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http://www.rsbird.com/ryan/ryan_mataway_overseeder.htm
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If you have someone aerate your turf, the Ryan LA-28 is tits.
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http://www.ryanturf.com/products/lawn_aerators/lawnaire_28/
