Download Roblox Player Launcher
To play Roblox on your PC, you will need to download the Robloxplayer.exe. This is a required download, because you can't play any Roblox games without it. Once downloaded, this file serves as an invisible launcher that will always take you to the Roblox client, opening your default web browser whenever clicked.
Download Roblox Player Launcher
After you have downloaded and installed the Robloxplayer.exe file, you can open any Roblox game on the platform. Some Roblox games require a one-time purchase of Robux, but you will rarely find a game that requires pay-to-play. Most Roblox games are free-to-play with the click of a button.
If you do, it's possible that Firefox isn't setup to automatically open the Roblox software when you press play. To check that, go to the Firefox options page and scroll down to the Applications section and search for the roblox-player content type. It should be set to Use Roblox.