When the player exits the Mars City Underground after the initial events of the demon invasion in Doom 3, R. Roland calls out from a ventilation shaft. He lowers a maintenance ladder, allowing the player to climb to his position. Having witnessed the shockwave that ripped through the base on Mars, he is frightened, and with good reason - he also witnessed the base's personnel being transformed into zombies. He implores the player to find help. If the player persists in speaking to him, he will strongly affirm that he doesn't want to leave his position in the maintenance shaft, believing it to be the only safe place, and further urge the player to find help.
While his fate is unknown, there is a possibility he would have lived long enough to be rescued at the end of the game, assuming he did not leave his hiding spot. However, according to the intro to Resurrection of Evil, the only known survivor of the incident on Mars is the player, implying that everyone else was killed off-screen during the course of the game (however Lost Mission does introduce other survivors). Considering that he was found shortly after the demon invasion began, he may have not lived long enough compared to the other survivors that the Marine encounters later on in the game. Also, at the end of the vent shaft, if you listen hard enough you can hear what sounds like him screaming, possibly because he was attacked by a zombie. However, there are also gunshot like sounds, meaning he either had a gun of some sort or it was someone else you heard (if at all).