Hello! I'm Jen, and I'd be happy to help you out with this issue.
I'm sorry to hear you're experiencing this issue. Do you have antivirus enabled? If so, it could be that the antivirus is blocking the installation process. Sometimes, the roblox installer encounters problems in gaining enough permission to access certain files needed for the installation to go through. Please try disabling your antivirus and see if it fixes the issue. Let me know how it goes. Thank you.
I hope this information helps. If you have any questions, please let me know and I'll be glad to assist you further.
Best Regards!
Jen :)