I'm stuck with basslines, cos whenever I come up with a good guitar riff I can never get a good bass riff to go with it apart from just repeating the root note of whatever chord the guitar happens to be playing at the time. but this just gets boring. Any idea's on how I can write better basslines that still go with the song?
Study some music theory, that generally does the trick.
just use the major or minor scale around the root note of the chord rather than testing every possible combination of notes. bound to spot sommat useful from that
Have some one else play the guitar line. Let them add their own touches to it. Listen to it a few times and try improvising while it's playing.
Major and minor scales and pentatonics are basically the heart of western music. Eventually as you look into more music theory you will learn other modes but for the time being, stick to major minor and pentatonics