Buy a Roblox Gift Card and share the code with them
Use the Roblox website or app to purchase Robux for your own account, then give them items or game passes if you control a game
Join the same Roblox group and use group payouts if you own the group and have Robux in the group funds
Create a game pass, shirt, or other item in your experience and have them buy it
Use the Roblox Premium Payouts system if you own a qualifying experience and they earn Robux through engagement
Trade limited items with them if both accounts have Roblox Premium and trading is enabled
Send them a gift card purchased from a retailer that supports Roblox gift cards