Hi Abel,
Your question about the balance of guitar is not entirely straight forward, it’s not overly prominent in the mix, but I feel that it may well benefit more from EQ’ing rather than simply increasing volume!
If you have tried the EQ cut don’t be too concerned if you don’t hear an immediate difference when soloing the guitar, it’s a step process where in this case the high cut should clean up the guitar in the mix and help it cut through. Don’t worry about individual strings at this stage either.
The next step is to get as close as you can with optimising the tone controls on your amp, what I find a good way of finding the sweet on an amp is to turn down all the tone controls, then turn each one up in turn until you start to notice a definite change and note where that setting is, turn it back down and then do the same with the next one, when you have finished set them collectively to those settings. Use channel 1 for this to keep it all as simple as possible, the same settings should apply to channel 2 for those particular controls as well as well, at the moment idea is to get a good start tone from the amps characteristics.
I’m familiar with Roland amps, but not that particular model, I had a look at some reviews and in this one it does indicate that it takes some experience to get the tones (see “What Do Other Musicians Think of the Roland JC-120 “ section):
https://vintageguitarmasters.com/roland-jc-120/I also found this video on Youtube which may be helpful for you, apparently it already has a parametric EQ and reverb:
https://www.youtube.com/watch?v=-bLx30P8wuEPlease let me know how you get on.
Regards
Gary