I'm using Roto SS on a GL Jazz and have pretty good results going for the Geddy tone.
First, you have to play really aggressively. There's nothing that will help if you don't nail that first. Also, getting the right setup makes a big difference. Action should be medium low. Too low and you can't play hard enough without too much clank. (a little clank is ok). Too high and you can't play fast enough to pull off any of the faster bits.
Geddy plays Roto standard gauge 45 to 105. I can't play as hard as I need to with that tension without ripping my pads off, so I back off and play the slightly lighter medium gauge.
Your amp makes a big difference too. A little OD blended in is vital. Geddy typically uses more than one amp (historically) or preamp (more recently) to get contrasting clean and dirty sounds.
Also, pickups play a big part. Geddy uses both pickups on full always. The Geddy Jazz is almost useless when it comes to mixing different pickup volumes due to hum. My answer was to replace the stock pickups with Dimarzio Area J pickups. They're close to the original in look, tone, and output, but the real benefit it to be able to use different volumes. I adjust my tone to get somewhere around the Counterparts (or later) sound with volumes full/full. And then simply by backing the bridge pickup down to half volume I get a very acceptable Free Will or Red Barchetta tone, and conversely by backing the neck pickup down to half volume (with bridge at full) I get a respectable Hold Your Fire, Presto, or Roll the Bones tone.
Having said all that, the best anyone is likely to do is to get close. I have many of the electronic bits and pieces available, and there is pretty good record available of what knobs to turn and such. But I find that as I get close to the sound I start to deviate a little bit and add my own preferences. Geddy allows for some space I his tone. I guess the other guys I his band are ok musicians and need to be heard every once I a while. I am under no such constraints and never met a frequency range that I didn't feel entitled to.
Good luck by the way. The sound you are going for is the reason why I enjoy picking up the bass every day. Just being in the neighborhood makes a world of difference.