Allen Roberts is the brother of Jason Roberts. A powerfully built man with ruggedly handsome face, and age beyond his years. His junior brother sees him as a father figure.
He is a top research scientist with endless curiosity and travels around the world to conduct work for Allister Research. He also arranged a job for his brother after he graduated.
He was at the Amazon River Basin to investigate unusual forest regeneration in slashed and burned areas for the Brazilian authorities. His team were hampered by Colonel Sanchez who insisted to send his men along for protection (actually espionage). They reached Sitio Maldito, an outpost that had been attacked by 'evil specters' with a small pool of radioactive liquid, which increased the speed of regrowth.
They camped on the 1st August and were harassed by eerie figures. More and more men deserted the camp. On August 10, at 2:06 AM the Allister camp was raided by strangers. Carlos was shot with an arrow in his heart and fell through Allen's tent. Allen slid through the back but also received an arrow on his shoulder but managed to fall in the river. Maya rescued him some days later and tended him in a hut.
Allen sent a letter to his brother Jason with instructions to find him. Maya met him in Rio Blanco and brought him to his brother to whom he recounted his story. After some days when he regained his health, the team walked to find Hans Stroheim.
The team was ambushed by a platoon of Sanchez' death squad near a gorge above Rio Dulce. Allen fended some of them off as Jason and Maya passed across the ancient rope bridge. When Allen was on the bridge, he was shot. To save his people and hold the adversaries away, he cut off the bridge and fell in the river.