roys lowest commitment move, dtilt, also happens to be your most rewarding move. So yes, this is generally the crux of your gameplan. however, there are other moves to consider as well. ill discuss as follows:
since dtilt is has such a low commitment (hitbox on frame 8, FAF on 20) its very effective to utlized spaced dtilts that are littered throughout your DDing. grounded characters generally have a near impossible time punishing it, andif you connect, then you get great reward. The only time dtilt approaches usually get punished are when you have a character that can outspace you (DDD) or if they have solid, ranged CC moves (DK, Zard, etc.). additionally, comiting to an aerial approach will be able to combat dtilt approaches. You have two additional tools that will each combat the counterplay for one of those scenarios: roys side be is a quick, frame 6 move with an FAF of about 30 i believe. it has great coverage above and in front of him, which makes it amazing for combating aerial approaches, while also getting great reward out of (subsequent hits, grab, etc.). The other tool you have is your grab, which obviously will combat a CC heavy opponent, and again, high reward. dash attack also exists, but is generally easily combatted through CCing or shielding. its best used more sparingly because of its commitment. other tools that can be useful, but maybe not as rewarding, are jab, ftilt, and sometimes spaced aerial approaches (just depends on the relative safety of the approach depending on the MU).
to summarize:
-dtilt can beat shielding (-5 on shield) and ASDI CC (ususally used by opponents that are on the move, aka not stagnant and already crouching) if spaced properly. also is very favorable for pressure against DD heavy opponents. beaten by aerial approaches, or extreme ranged options
-side b can beat aerial approaches and shields (by properly spacing and varying sequence of your hits), but is heavily beat by CCing
-grab beats CCing, but is stuffed by ranged attacks or proper DD usage
-jab, ftilt, and dash attack will all lose to CC, but have niche uses in speed (jab) and ranged pokes (ftilt or dash attack)
-aerial approaches can beat projectiles, and shields if spaced, but lose to CC and DD
generally, characters with effective CC options that also outspace his grab range, or that can grab him within CC range, are the ones that beat roy. DK beats roy because of a great CC (heavy weight), and his neutral options are very effective at outspacing roys grab range (mainly dtilt). this allows DK much safety in focussing on CCing, and in turn getting a grab (he has a pretty good grab range), and thus heavily punishing you. he also will generally outlive you. This makes neutral hard for roy, as well as securing a stock, while he simultaneously has stocks taken pretty easily. Charizard is in a very similar boat as DK. DDD as well, but he just has many options that purely outspace roy, and his neutral game is largely air centered, not ground, which makes roy usually have to approach, and generally succumb to better disjoint on DDDs part. again, DDD lives forever, has a great gimp game, and roy is very fragile.