EDIT 06/20/2023
As of the same date of this edit, Roblox has officially moved to ban simulated gambling by September 18th, 2023 (in 3 months), which means that all forms of gambling are no longer allowed on the platform. This contrasts the prior stance to which, as long as there was no Robux involved, it could be passable.
The advice in this post is no longer accurate. Please avoid sharing this as an answer. For more information, please see Updating our policy on simulated gambling in the thread Create Experiences for People 17 and Older on Roblox.
Spinner systems are circumstantial. You may end up needing to follow a different policy if the spinner always guarantees that players will win items and there is Robux involved. Most spinners typically fall under paid random virtual items but if there’s a losing option in which the player gets no items after payment then that would fall under the gambling policy.
Keep in mind that gambling and paid random virtual items adhere to two different policies on the platform (cc @souppression) and are primarily dictated by the involvement of Robux as far as moderation is concerned. You need to be very clear and concise with how you offer advice on these threads, as some minor details can be left out (cc @KdudeDev).
Here’s a handy chart I drew up regarding this situation. The colour schema might be bad for dark theme users so I apologise, I use DevForum white theme. I’ve included a white background so you can open the image in a new browser or zoom in to see the items.
Transcribed in matrix format:
| Robux involved? | Guaranteed an item? | Policy to follow |
|---|---|---|
| No | No | N/A |
| No | Yes | N/A |
| Yes | No | Gambling |
| Yes | Yes | Paid random virtual items |
So answering your question, what does Roblox define as gambling? That is specifically the use of Robux directly or by proxy on a paid random item generator where it is possible for the item generator to generate nothing (a losing result). This is explicitly outlawed on the platform and will result in moderation action against your account.
On the other hand there’s another policy, paid random virtual items. This policy is in effect if it is possible to always win an item from your random item generator. In that case, you may keep it up but you must disclose the exact numerical odds of obtaining an item from it if Robux is involved directly or by proxy. The Developer Hub has an article on it, Virtual Items Policy, in addition to the announcement thread as linked in the post above which contains the important information.
In-game currencies classify as Robux use if the currency can be purchased with Robux. If your in-game currency is only obtainable through completing tasks and playing the game then it does not constitute as Robux or real currency use and you may freely put it towards gambling as well as lootboxes without the chances of winning certain items from it disclosed.
I wrote another lengthy post a while back that explains the circumstances as well, but if you’ve read this far then that post is essentially an echo of what I wrote above. Check that out here:
Keep in mind that Roblox does not police content, so games with gambling/undisclosed odds on lootboxes are either in accordance with the policies or have not been brought to moderation attention. You can help moderation investigate these cases by using the Report Abuse feature.