There are very few descriptions of trolls in TLOTR. The troll that the Fellowship encounter in Moria has "a huge arm ... with a dark skin of greenish scales [and] a great, flat toeless foot". The mountain trolls who are intended to wield Grond in the siege of Minas Tirith aren't described at all.

None of them are anything like the vaguely comedic trolls in The Hobbit.