almighty, deafening, ear-splitting, great, huge, loud, mighty, thunderous, tremendous
The lion let out a great roar.

angry, fierce, terrible
The shouting grew into an angry roar.

deep, low
dull, faint, muffled
throaty
the throaty roar of the engine

distant
the distant roar of the sea

sudden

give, let out
hear
become
The low rumble had become a roar.

erupt, go up
A mighty roar went up from the crowd as the home team scored.

echo
The sound of a distant roar echoed over the plains.

fill sth
A loud roar filled the air around them.

above the roar, over the roar
She couldn't make herself heard over the roar of the engines.

with a roar
The car sped off with an almighty roar.

roar from
There was a crash and a roar from the kitchen.

roar of
a roar of applause
a roar of laughter

Roar is used with these nouns as the subject:
audience, cannon, crowd, engine, fire, flame, lion, monster, thunder, tiger, traffic, wave, wind

Roar is used with these nouns as the object:
approval