Roundtree rhymes with:
baytree, braintree, crabtree, doubletree, grantree, lanktree, lonetree, ogletree, palmertree, peachtree, rooftree, rowntree
Roundtree sounds like:
rainwater, rander, reenter, reentry, reindeer, remainder, reminder, render, renter, renteria, rinderer, rounder, rountree, rowntree