It’s not immediately clear whether you’re asking about NoCopyrightSounds (NCS), the music recording company or just non-copyrighted audio in general, mostly due to the capitalisation and unrelated terms proceeding afterward. I’ll do my best to answer both sides anyway.
Something I see in your thread is that you’re asking about Roblox’s policies about use of NCS in games but you haven’t asked about NCS policies about use of tracks in games. Roblox’s policies and NCS are different. You need to consider both sides of the equation before going forward.
The title of the company, NoCopyrightSounds, may be misleading to some developers in terms of acceptable use so it’s always important that you confer with licensing or usage policies on their websites before using them. If you aren’t able to find this information immediately, try to find a point of contact and touch down with them.
Roblox’s policy on audio use is that you are permitted to use 250 APM tracks or any track of your own choosing provided you have a license or permission to use the song. If it is removed from the site, you may dispute with evidence via appeals. More information can be found through the various announcement threads discussing audio.
As for NCS, you actually require a commercial license in order to be able to use their music for your games. Commercial licenses typically are used for anything where purchases are involved (e.g. products and services), however game use falls under commercial use according to their licensing, whether it is free to download or not.
NCS Usage Policy:
https://ncsmusic.com/usage/
Excerpt:
Can I use NCS music in my independent video game?
Regardless of whether your game is free to download, use of our releases in video games is considered to be a commercial use. A Commercial License Agreement will need to be signed between NCS and Game Developer / Publisher.
As for just non-copyrighted sounds in general, same thing, Roblox’s policies are more of a paraphrase than anything. It’s up to you to look for any licenses or ensure that what you’re using doesn’t have any specific restrictions placed upon it. If the audio isn’t public domain then realistically you should be obtaining a license or permission for its use.
Your ability to DevEx is not related to your use of audio tracks in games unless you start earning strikes, as the audio itself will just be deleted and you’ll have to find a new one to use. That being said; yes, you are allowed to use any track with respect to its licensing situation.