If your anti-virus has flagged Roblox as a concern, please rest assured that Roblox is virus free and does not contain any malware. Occasionally, antivirus programs may flag a program incorrectly, which is known as a false positive. Here are some suggested solutions to help prevent that from happening, as well as what you can do if it occurs:
Update Your Anti-Virus
Sometimes all that you need to do is just make sure that you have the most recent version of your anti-virus program. It's possible that they have already patched the problem. If this doesn't work, then let's move on to the next possibility.
Flag The Report as a False Positive
If updating the software didn't help, then you'll need to flag the warning as a False Positive. To ensure that the Roblox program is able to run correctly, you will need to set it as a permitted program for any anti-virus or anti-malware application. This can be different for each program, but the below links may be able to help with some of the most common ones.
When searching for exclusions on Windows machines, Roblox files are stored in the following folder:
C:\Users\(Your Windows Username)\AppData\Local\Roblox