Few children's films seem to get serious scores, which is why you won't see many on the list suggested for roleplaying. There are a few exceptions such as Goldsmith's score to Mulan, but has too many songs to make it worth while. The Land Before Time is different because it only has one song, and has Horner scoring hot off his work for Willow.
Though comical in areas, on the whole The Land Before Time is quite a good score. Grand and sweeping in areas, touched with a little action and a little adventure. Well worth using when you need a bit of background music for the characters' exploration attempts.
Because the tracks are so long, I would only recommend using the music in the background. The score is fairly generic so you could use it in either fantasy or science fiction adventures. I'd tend towards fantasy myself.
Horner at his more original best.
Track Listing and Notes
The Great Migration (7:52) - opening ~ journey ~ exploration
Sharptooth and the Earthquake (10:35) - lonely ~ discovery ~ chase
Whispering Woods (9:03) - hope
If We Hold on Together - Diana Ross (4:10)
Foraging for Food (7:18) - exploring
The Rescue/Discovery of the Great Valley (12:46) - journey ~ happy