The lanes toward Shore Acres roll more than a coastal town suggests — short rises, long soft slopes, lawns falling away from the house toward the trees. Rolling Lawns Inc. mows that ground in Mamaroneck all season, following the contours instead of fighting them, trimming the ragged edges and clearing up in spring and fall. June is the real test, when growth outruns the schedule and a week's delay shows immediately. A lawn cut with the roll of the land looks like one sheet of green from the front step. Earning that on uneven ground is the part worth doing well.