The online video game purveyor is apparently not doing as well as it could in the sale of its in-game currency.Growth concerns raised by an analyst tracking Roblox (RBLX -7.95%) stock affected investor sentiment on Friday. With that tailwind, market players traded out of the online video game company to leave its shares with a more than 8% decline on the day. By contrast, the S&P 500 (^GSPC 0.01%) essentially traded sideways.Analyst points to slowing bookingsThat morning, M Science's Corey Barrett wrote a f ...