A little bit late, but I'm going to address OP's question first. With Roy, you typically want to spend a majority of your time mastering movement and punish game. However, if you're not used to Roy yet, spacing is a big must for you to practice.
Though, to play Roy successfully you need to be very disciplined in a lot of the stuff you do and need a strong understanding of Roy's grounded-air transitions. You need to get pretty good at utilizing your grounded moves, which is the basis of having a strong movement game. Too many Roys get into the air too much, which is a huge reason they're not successful. To elaborate, when you go in the air, your mobility is compromised and you don't have access to some of your better grounded options, such as shield, Down-Tilt, Jab, F-Tilt, Grab etc. To exercise good movement, you have to build respect with a strong grounded game, so they don't just run-up and hit you. What stops them from running-up and hitting you is the fact you can put out a hitbox. This mutual respect between you and your opponent allows you the space to move well.
Anyways, aside from that you don't need C-Stick N-Air to use N-Air to its fullest potential. You can kill confirm just fine using regular N-Air. The only reason you need C-Stick N-Air is to frame cancel into F-Smash, which is hard to get consistently. If you master it, it's really good, but it's not necessary and being a successful Roy.
While Nair is useful, it doesn't matter much if you can't play the neutral right. It is more important to find an opportunity to capitalize on an opponents mistakes with safer, guaranteed options. The full potential of Nair is great, but it is rather situational from my experience.
If anything, you should figure out an effective way to bait and punish, since Roy's neutral is poor due to his lack of range, poor approach, and struggling against zone based characters.
I have to disagree with this. Roy's neutral is really amazing, it's just really complex, and you need to understand that you can't expect to win by SHFFing all over shield with Roy. There's no character who should be allowed to win neutral by SHFFing all over the place and winning. In fact, there's no character in Smash history that wins by SHFFing all over the place and winning.
N-Air is a great move with a large variety of uses, which is the complete opposite of situational. If you use N-Air effectively, it's a frightening hit confirm that can convert into a guaranteed ~40-60% combos and more. However, you need to mix it up with tomahawk grabs, cross-ups and other moves to make full use of Roy's ability to keep his opponent on edge. Being able to establish that SH N-Air is something to be respected, your opponent will start shielding it. Your opponent needs to position themselves far enough to react to it, giving Roy the space to move around. Which is how you create space that allows you to Extended Dash Dance with Roy. It's not Roy's fault if you get punished for N-Air'ing on shield. If they're respecting your N-Air with shield, it's your opportunity to grab them and get even scarier conversions.
While it is true that you should always strive for safe and more guaranteed options. N-Air in itself is a safe and guaranteed option. If there's a stronger option, of course you should choose it. But, N-Air is one of Roy's strongest options.
Bait and punishing is a dimension of Roy that one should master, but one should also master trapping his opponent, conditioning and zoning them for several situations.
I don't think Roy has what constitutes as a poor neutral. His Down-Tilt is safer than Diddy Kong's being +2 on shield. In fact, most of his aerials are + on shield. Furthermore, you need to understand Roy's moves have quite a bit of shield pushback, like F-Tilt isn't punishable due to the space it creates on shield. Or B-Air, which is - on shield, but has a lot of shield pushback making it safe.
Furthermore, I disagree with Roy struggling with zoners. Roy's property of having amazing airspeed allows him to close space well, which mitigates his lack of range. He covers space through his speed rather than with his raw sword range. That's why maintaining momentum and movement is good for Roy.
If your Roy is struggling with zoners, you need to be more disciplined about shielding and taking space. Lastly, Roy doesn't struggle with approaching because he does a good job influencing the space between him and his opponent.
Strictly speaking, the definition of approach is a blanket statement that has been diluted to the point that approaching is bad and not approaching is good. People think of approaching with unnecessary commitment, impatience and overextension. However, games are not broken down into such extremes.
Roy, and to an extent all characters, can approach. This is what creates footsies, because the importance of positioning forces engagement and interactions between characters. All characters need to approach to eliminate options in neutral and create potential options. Since Roy covers space well and has a sword, he's naturally good at preventing options, whiff punishing well and get out of the way for potential openings.
Sorry this was kind of messy, since neutral is an abstract concept to explain. But, Roy has all the tools for a controlling and dominant neutral game.
