Even though it was designed by wargamers the fact it was Star Trek meant a lot of role-playing came along for the ride. Some of the best campaigns I ever refereed was using FASA's ST:RPG.
The best adventure I ever ran involved the players starting out on a milk run dropping navigation warning buoys around the time-space distortion that nailed the USS Defiant and nearly got the USS Enterprise. The ship, the USS Challenger, was refitted with a emergency anti-matter injector that could give a short burst of Warp 9. It was done in case there was a problem with the ship falling into the distortion.
I went all out for my Star Trek games. I used what computer tech I had at the time and creative photocopies to create orders, manifests, and other in-game documents for my players.
When they were halfway done, the distortion starting grew unexpectedly and caught the Challenger. The Engineer made his skill roll and injector worked pulling them out. When sensors came back on-line the Science Officer reported a Klingon D-7 bearing down on the Challenger with shields up. The players had a tough fight but the lone D-7 was no match for a Consitution Class Starship and it fled.
During the course of doing Damage Control after the battle, Comm Officer reported the Subspace Network was down. The Science Officer, Engineering and Comm Officer worked together to determine what was going on. The Challenger equipment was OK but the Subspace Network was simply gone. Even nodes near the Federation's Core were not on-line. However when they started searching for the other races they began to pick up a unknown network centered on Andoria. They found the nearest node and warped to it.
When they got there several weeks later they found a Starbase of unknown design. When they made first contact they discovered it was a Starbase on the frontier of the Andorian Star Empire! By now it was obvious they were thrown in some parallel timeline.
The players were able to find out that the Andorians had no record of Humans or Earth. The only record was that they found a dead world destroyed by nuclear weapons. As a consequence the Federation never developed and the Andorian Star Empire now dominates this region of space contending with the Klingons and Romulans for power.
They were able to secure permission to proceed to Earth. When the players got there they beamed down and started combing through the ruins for any records of what happened. They were surprised by Klingons and a firefight ensued. Meanwhile in orbit the Challenger was attacked by a D7 hiding behind Earth's Moon. It was a tough fight but the players won both on the ground and on land. The D7 was destroyed in the aftermath.
The players were able to determine that the nuclear war occurred around October 1962. Apparently in this timeline the Cuban Missile Crisis exploded into World War III engulfing the entire planet in nuclear war leaving on the cockroach as the highest lifeform.
From the wreckage of the D7 they were able to find out that the D7 was sent to the time-space anomaly that the Challenger was mapping and was able to use it to go back into time. They launched a nuclear missile at the US Fleet blockading Cuba. Both sides blamed the other and the crisis spiraled out of control into full scale war.
A smart player checked and it turned out the Challenger had the data on-board to execute a time warp via a slingshot around the Sun. What followed was some of the best roleplaying I ever seen as the players debated among themselves whether it was ethical to go back and restore the time line. This debate elevated a pretty good session into a game that emulated it's source material perfectly. Both sides had strong points in favor of the arguments. Both arguing with the passion that only college age fans could bring. In the game billions of lives were at stake on the decision. The player of the Captain actually started sweating at having to make this decision.
In the end the decision was to restore the timeline. The Challenger slingshotted back to 1962 and hide behind Earth's Moon. When the Klingon D7 warped into Earth orbit the Challenger surprised it and was able to destroy it before it launched the missle the ignited World War III. Then it warped back to the 23rd Century back into a future where the Federation existed.
And that was the best damn game I ever ran.