You cannot directly send Robux to a friend from your balance
Buy a Roblox Gift Card and give the code to your friend
Purchase a game pass or item from your friend’s Roblox game if they created one
Buy their clothing item if they made one and set it for sale
Use a group payout if you both are in the same Roblox group and you have permission to distribute funds
Make sure any transaction follows Roblox’s rules and is done through official Roblox features