Short answers, pulled from the story.
Marcus Licinius Crassus arrived in Syria in late 55 BC. He immediately used his immense wealth to raise an army consisting of seven legions and approximately 28,000 to 35,000 heavy infantry.
The battle began when reconnaissance found scouts slain and a large force of cavalry approaching near the town of Carrhae. The Parthian commander Surena used horse archers to surround the Roman square while cataphracts exploited weaknesses in their testudo formation to inflict heavy casualties until nightfall.
Crassus died during a meeting with Surena where a Parthian pulled at his reins and sparked violence that killed him and his generals. After his death the Parthians allegedly poured molten gold down his throat as a symbolic gesture mocking his notorious greed.
The 10,000 Roman prisoners of war appear to have been deported to Alexandria Margiana near the Parthian Empire's northeastern border in 53 BC. They reportedly married local people and may have fought as mercenaries at the Battle of Zhizhi between the Chinese and the Xiongnu in 36 BC.
Marcus Licinius Crassus refused the offer possibly because he felt Roman forces were enough and may not have trusted Artavasdes completely. He decided to take the direct route through Mesopotamia in order to capture the great cities in the region despite warnings about the desert terrain.