Answered by: Aalimah Nasima Umm Hamza
Assalamu Alaikum Wa Rahmatullah
Is Roblox haram?
بسم الله الرحمن الرحيم
In the name of Allah, the Most Gracious, the Most Merciful.
In essence it is permissible.
However, we must be cautious about how we use our time as we are accountable for how we use it. Computer games are a source of wasting time as hours can go by playing game after game.
The Prophet (PBUH) reminded us to make use of five things before five other things, and one of them was our free time before we become occupied. 
As well as this, there are other people online who may exhibit immoral behaviour and conduct, which must be avoided.
Only Allah Ta’ala knows best.
Written by Aalimah Nasima Umm Hamza
Check and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Al-Bayhaqi, Sha’b al-Imaan, Hadith 9575
This answer was collected from DarulIftaBirmingham.co.uk, which is run under the supervision of Mufti Mohammed Tosir Miah from the United Kingdom.