Rosenblatt starts coverage on Robinhood with 'buy'; shares gain

** Robinhood Markets HOOD.O shares gain 2.5% to $100.68 in premarket trading

** Rosenblatt Securities initiates coverage on stock with "buy" rating, PT $135

** Views co as "one of the best growth stories in the financial sector"

** "What started as a commission-free trading app has become a full financial platform, the market still under-appreciates how much the story has matured," brokerage adds

** Twenty-six of 32 brokerages rate the stock "buy" or higher, five "hold" and one "sell"; their median PT is $136 -LSEG-compiled data

** Up to previous session's close, shares down 13.2% YTD