These cost $2000 more than a Pool Cleaner because the Pool Cleaners only cover two lanes while the Roof Cleaner covers five. The Roof Cleaners' unit price is $600 while the Pool Cleaners' is $500. The increase in unit price is most likely because this increases money received at the end of the stage while the Pool Cleaner doesn't (because it only replaces the Lawn Mowers).
Over time, these can earn money for the player. This is because, without them, there is no bonus available at the end of each level. Once purchased, players earn $50 for each remaining one at the end of each roof level. Hence, after 12 "perfect" roof levels, he or she will have earned back the full cost of them. This doesn't apply to Pool Cleaners, as they merely replace the existing Lawn Mowers for the two pool columns.
When this happens, a biting sound is heard, despite not being eaten. However, this may simply be a crushing sound as the same instance happens to other zombies like the Zomboni, Catapult Zombie, and Gargantuar.
It will not change its appearance when "trickedout" is typed.
This is because "trickedout" only applies to Lawn Mower, not Pool Cleaners or Roof Cleaners.
However, the sound of the car starting is still heard.
As they are found on Roof levels, because of the roof's slope, this will slant upward, unlike the Pool Cleaner or Lawn Mower as they never appear on sloped levels.
It will slant to the right because it is a 2D image meant to look like 3D, so in the real world, it would move slanted to the right.
If a zombie makes contact with a Roof Cleaner, it will drive down the lane and run over any zombies it meets. This is true for Gargantuars (and Giga-gargantuars) as well, even though other instant kills, such as Squashes or Cherry Bombs, are only able to get rid of 90 points of their health. This may suggest that the Roof Cleaner, as well as the Lawn Mower and Pool Cleaner, are the strongest weapons in the game, or the second strongest, considering that the Giant Wall-Nut can defeat Dr. Zomboss (observable if he was hacked to appear in wall-nut bowling 2) while the roof cleaner has no effect on him.
The most obvious reason for a lawn mower not to appear on the roof is that it's construction is rear heavy and when it is launched, the machine will simply tilt backwards and fall from the roof, unlike the roof cleaner which is perfectly balanced.