we know based on the Hobbit mountain trolls can talk,but can trolls in Mordor (Olog-Hai) speak in the same tongue as the peoples of Middle Earth? or do they just grunt and roar like we see in the movies only?
According to Appendix F to The Lord of the Rings, they don't "grunt and roar", they are capable of speech; but they do not speak in the Common Tongue or any other of the peoples of Middle-earth:
Trolls they were, but filled with the evil will of their master: a fell race, strong, agile, fierce and cunning, but harder than stone. Unlike the older race of the Twilight they could endure the Sun, so long as the will of Sauron held sway over them. They spoke little, and the only tongue that they knew was the Black Speech of Barad-dûr.