I wouldn’t call this matter “routing” but “assigning”. Your problem is that your drum set hasn’t got enough drum pads to assign the astounding number of kit pieces Legacy of Rock SDX includes in its Amber Kit. I don’t think there’s one drum kit in the market with so many pads as to control every kit piece there. I’m not into MIDI Drum Kits (I program my drum beats, bass & guitars, since I’m a keyboard player myself). But there’s a workaround for you (a good friend of mine used to do this to add additional pads to his MIDI drum kit) if your Roland Drum Kit uses standard MIDI in/out cables, and, of course, you use that to plug it to your computer’s audio device, you could try getting a cheap, second-hand MIDI Drum Pad (these usually have 4 pads) with assignable MIDI notes for each pad (you need to be able to assign these to the required MIDI notes) – that would give you 4 additional pads to play (granted, they may not have the same sensitivity as your Roland Drum Kit Pads). Then, plug the MIDI OUT of this additional MIDI Drum Pad to the MIDI IN of your Roland Drum Kit through a standard MIDI cable. And then, the MIDI OUT of your Roland Drum Kit to your Audio Device’s MIDI in.

If your Roland Drum Kit is plugged into your computer via USB, you could use an additional MIDI Drum Pad anyway. Just plug it into your computer (either via USB or standard MIDI in/out) and within your DAW, set your Superior Drummer 3 track to receive data from ALL MIDI INPUTS. (At least, Cockos Reaper can do that – and you can even set Reaper to send all received MIDI notes to the same MIDI channel, even if they come as, say, channel 1 notes from one device and channel 10 notes from the other).

I hope this might have been of help for you.

Kind regards from Spain. Stay healthy and keep safe.