3 letters:
kol, roa, rol

4 letters:
boal, bohl, bole, boll, bowl, buol, coal, cole, dole, foal, fohl, goal, gohl, hoel, hohl, hole, kohl, kole, mohl, mole, nohl, nole, noll, pohl, pole, poll, rael, rahl, rail, rall, raul, rawl, rayl, real, reel, reil, reul, riel, rile, rill, road, roam, roan, roat, robe, rode, roed, roen, roes, rohm, rohs, roil, rolf, rolm, rolt, rome, rone, rope, rose, rote, rove, rows, ruel, ruhl, rule, ryle, sohl, sole, soul, toal, tole, toll, wohl, role, roll

5 letters:
boehl, coale, colle, croll, dhole, doell, droll, foale, groll, hoell, knoll, koehl, noell, pfohl, poehl, raile, rayle, reale, reihl, reule, rhoad, rhode, rhome, rhone, rhule, riehl, roach, roald, roane, roath, roche, roehi, roehm, roese, rogue, roh's, rohde, roher, rohlf, roles, roley, rolfe, rolls, rolly, rolph, roque, rothe, row's, rowed, rower, rowes, rowly, rowse, royle, ruehl, ruyle, seoul, sowle, thole, troll, voell, whole, woehl, wrote, roehl, roell, rolle

6 letters:
hoelle, knoell, koelle, proehl, roache, roelke, roesch, roll's, rolled, roller, rollie, rowe's, rowell, rowles, rowley, rowlie, schaul, thoele, toelle, roelle

7 letters:
roeller, scholle, schroll