Exhibit 5.1

Wilson Sonsini Goodrich & Rosati
Professional Corporation 650 Page Mill Road
Palo Alto, California 94304-1050 o: 650.493.9300
f: 650.493.6811

February 21, 2024

Roblox Corporation

970 Park Place

San Mateo, California 94403

Re:Securities Registered underRegistration Statement on Form S-8

Ladies and Gentlemen:

We have examined the Registration Statement on Form S-8 (the “Registration Statement”) to be filed by Roblox Corporation, a Delaware corporation (the “Company”), with the Securities and Exchange Commission on or about the date hereof, in connection with the registration under the Securities Act of 1933, as amended, of an aggregate of 37,873,280 shares (the “Shares”) of the Company’s Class A common stock, par value $0.0001 per share, consisting of (i) 31,561,067 shares of Class A common stock reserved for issuance pursuant to the Company’s 2020 Equity Incentive Plan and (ii) 6,312,213 shares of Class A common stock reserved for issuance pursuant to the Company’s 2020 Employee Stock Purchase Plan (which plans are referred to herein as the “Plans”).

On the basis of the foregoing, and in reliance thereon, we are of the opinion that the Shares, when issued and sold in the manner referred to in the Plans and pursuant to the agreements that accompany the Plans, will be legally and validly issued, fully paid, and nonassessable.

We consent to the use of this opinion as an exhibit to the Registration Statement, and further consent to the use of our name wherever appearing in the Registration Statement and any amendments thereto.

Very truly yours,

WILSON SONSINI GOODRICH & ROSATI

Professional Corporation

/s/ Wilson Sonsini Goodrich & Rosati, P.C.

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