Cover Page - shares	9 Months Ended
	Sep. 30, 2023	Nov. 01, 2023
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2023
Document Transition Report	false
Entity File Number	001-39763
Entity Registrant Name	Roblox Corporation
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-0991664
Entity Address, Address Line One	970 Park Place
Entity Address, City or Town	San Mateo
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94403
City Area Code	888
Local Phone Number	858-2569
Title of 12(b) Security	Class A Common Stock, $0.0001 par value
Trading Symbol	RBLX
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001315098
Common Class A
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		573,650,725
Common Class B
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		50,086,273