Rolling a lawn with...

Do you mean trying to level the soil to lay/sow a lawn, or on an existing lawn.

My guess is that a wacker plate would be a bit brutal, especially on existing grass (I'm not sure that routine rolling is a very popular practice these days anyway, possibly because it can over-compact the soil, which is the opposite of what you are usually trying to achieve.)

I think a wacker plate will damage the grass shoots (and probably cause unwanted ground compaction). How big are the humps and bumps? Could you consider filling in dents with soil to bring the level up, or lift the turf in high areas to scrape soil out?

I am no expert, but have read that rolling is no longer used to level lawns, unless you want to bounce a hard ball off it

I laid mine last year and it is now a bit bumpy so will go over it with a fork to reduce compaction and add a bit of sieved compost mixed with seed as it's a bit patchy when you get close to it.

I think a wacker plate will damage the grass shoots (and probably cause unwanted ground compaction). How big are the humps and bumps? Could you consider filling in dents with soil to bring the level up, or lift the turf in high areas to scrape soil out?

The humps and bumps have been caused by our chooks. 

Them getting a bit over zelous in one place. Just thought of filling them in, rather than a whole turfing.
If I filled them in with seed mixed in with soil, the chooks would just scratch it back out.

And I don't want to have them locked up until the grass gets established....