#1
I recently picked up my first electric (Epiphone Les Paul Tribute) and amp, which is the Roland Cube 20GX. I've tried playing a couple of songs and I can really well, but I can't seem to get the right sound for a lot of them, like R U Mine, by the Arctic Monkeys or No More Lies and Shoot To Thrill, by Iron Maiden and ACDC respectively. Could anyone help with settings, even if it's just a generic crunchy sound?
#2
I owned a Roland Cube 20GX for a while. In my opinion, the JC Clean channel is the amp's best feature. I found the other 'dirty' channels sounded cheesy and stereotypical. Quite surprising considering this amp is made with Boss technology. A fun little practice amp nonetheless and produces respectable levels of volume to boot. Did I just type "to boot?"

A classic general setting I like to use from time to time includes low 4, mid 6, hi 8, gain to personal taste.

If you are looking for crunch, the general rule is turn up the lows and highs while cutting the mids. An extreme crunch would be low 10, mid 0, hi 10, gain 10. I found a Jimmy Page setting described as low 7, mid 3, hi 8, gain 4. Jack White was listed as low 8, mid 5, hi 7, gain 8. I found Angus Young settings that were low 4, mid 10, hi 10, gain 4.

Hope I was able to be of some help in your quest for tone.
1984 Yamaha SG1000X
2006 Epiphone Les Paul Black Beauty 3
2011 Fender Mustang IV
2011 Gretsch G5120 Electromatic
2014 Fender Mustang I (V.2)
2016 Gibson Custom Shop Standard Historic 1957 Les Paul Goldtop Reissue VOS
#3
Invest in an inexpensive distortion pedal and run it thru the clean channel. This will be a huge improvement.