Well, as an experienced bass player (23 years of playing) i have to mention that
a) sone of the songs, and that even includes some originals and official dlc's, have somewhat incomplete bass lines. You can hear that where the notes in RS tell you to play for example the root note of a chord for a whole measure, the bass in the backing track sometomes actually moves - sometimes even a lot. That may just be a low fifth or an octave, but sometimes whole runs are simply not transscribed. The reason is imho that the bass lines in the guitar pro files (which i also use) are not correctly made, so no offense to our cdlc creators.
b) a lot depends on the songs you choose to play. If you're mainly into mainstream stuff the bass is quite often pretty much straight root notes in a simple rythm. Sometimes there are some ear friendly runs, but even then its kept rather simple.
c) picking speed on the bass is most of the time a lot slower than on the guitar
d) there are almost no chords in the bass lines
e) to quote my bass teacher: "you earn your money with the first fife frets". A lot of arrangements in RS can be rearranged on the fly to be played exactly there. Why jump to the tenth fret on the e string when you can play an open d string instead if not for a slide?
f) much better fretboard overview on the bass than on a guitar
g) a bassists job isnt to shine or pose or show off. It's carrying the music in conjunction with the drummer.
That said, you might wanna try some arrangements from chili peppers or early, buton aera Metallica if you want a challange on the bass. There are others, but i'm at work and dont have access to the song list of RS.