For clarification on forward roll,
I "get away" with a lot of forward rolls because it's actually an incredibly useful tool for getting past metaknight's ground game. It's particularly useful if mk likes approaching with walk-> forward tilt (which many do against pikachu because for some reason people think it ***** him) because it's well ranged enough to get behind him and quick enough to let you punish.
I've messed with the timing enough to get past d smash (funny thing is the second swing comes out before you actually get behind him and I think invincibility protects you from the first swing), which is particularly useful when they like doing f smash-> d smash on your shield. I've even used it to get past forward smash (the spacing is reaaaaaally tight and sometimes I end up in front of them as a result).
While it may not be a great answer to down tilt, I've noticed people in general really hate it when people are behind them (particularly when they're in shield) and often they'll show some sort of bad habit to try and get out of that situation (spotdodge, roll, etc).
And of course it's another option to get past grounded shuttle loop, and I'll buffer it after say a SH down air because quite frankly he just doesn't expect it and is too slow to punish as a result (he'll usually expect a spotdodge or shield so he'll just try to grab).
I definitely need to cut back on it, but I assure you I use it less against people who aren't Trevonte. He just personally has a weakness against rolls ;o