You cannot install Roblox on a Nintendo Switch Lite
Roblox is not officially available on the Nintendo eShop for Switch
There is no supported way to sideload Roblox onto a Switch Lite
Use Roblox on a phone, tablet, PC, Mac, or supported console instead
If you want to play on a handheld device, use an iPhone, Android device, or a Windows laptop
Check the official Roblox website or Nintendo eShop for any future release updates