The cheap rollers in this price range are mainly sand or water-filled polyethylene devices - but don't be put off by their low price as they are all capable of creating a beautifully flat lawn.
Admittedly they wouldn't be up to tackling a huge lawn - that would probably call for a tow-behind roller - but they will be very capable of getting a small to medium-sized lawn looking level and tidy.
An obvious benefit of a water-filled poly roller is there is no risk of the drum rusting and also they can be emptied after use and easily pushed to a shed or garage until needed again.
These rollers can take on a multitude of other tasks including levelling mole hills, mounds and other unsightly protrusions which are stopping your lawn from looking just right.
A roller also does a great job a pressing newly-sown grass seeds firmly into the ground - simply scattering new seed and leaving it is not a good idea as it is easy for hungry birds to enjoy a free snack. There's also a risk of it blowing away in the wind.
Some of the rollers in this price range have a handy scraper bar fitted along the front of the device to catch loose debris which is gathering on the plastic or metal drum.