Action (Centered around combat between players. Single-player action games are rare. Generally less popular on Roblox than other platforms.)

Survival (Players attempt to survive or escape external obstacles, such as environmental hazards.)

Customization (Common central mechanic where gameplay is focused on looking for customization options. Often found in the context of 'dressing up' and shopping for clothes.)

A roleplaying game that resembles playing "house". (Brookhaven, Islands, Jailbreak)

A deeper version of "cops and robbers". (Brookhaven, Islands, Jailbreak)

Hide and Seek (Players hide from an enemy, either controlled by another player or non-playable character. Often combined with puzzle elements or obstacles.)

Obby (Shorthand for "obstacle course" and known on other platforms as a "platformer". Requires players to climb, jump and navigate obstacles to reach the end of the course.)

Bee Swarm Simulator

Roleplaying (Often focused on building and exploring, with some including content from other genres. Typically more expressly oriented around imaginative social roleplaying than story-based 'RPGs' on other platforms.)

Gives users a building set, similar to Legos. (Brookhaven, Islands, Jailbreak)

Tycoon