This group is taken from the 28mm plastic 'Russian Heavy Weapons' set, Plastic Soldier Company (PSC). For a proper review, although of the 1/72 scale kit version, take a look at the Plastic Soldier Review site (click here).
"Use this natural, realistic product to model fallen or standing dead trees and stumps. It has the look of aged wood with gnarled branches, knots with some smooth, weathered pieces."
Or, as I've just said, you can pop outside, look under a tree, bush or hedge and grab a handful of dead wood for free.
The roots are simply made by twisting a suitable length of tissue paper. Glue one end, (you'll have to use super glue) near the stump. Once dry twist the tissue paper again and carefully glue the other end into position, being careful to avoid gluing your figures to the base (not like I'd be daft enough to do that, of course). Then apply super glue over the length of the paper to set it so that it doesn't unwind itself. Simple as that.
The most notable problem with this set is that there isn't any ammunition being fed into the machine gun. This would be less obvious with the 1/72 scale version but I will have to add an ammo box and belt sometime in the future.