The Comcast - Time Warner deal may be bad news for some TV streamers.

Comcast users won't be able to use many of the popular streaming services through a Roku - a device that accesses services like Netflix and HBO Go.

Currently, Time-Warner customers can get those and watch Time Warner cable through a Roku, but Comcast blocks outside streaming to HBO Go, Showtime Anytime and other services, and once Time Warner becomes part of Comcast, those users will be locked out too. Roku says it's sold close to 8 million devices in the U.S., and accounted for more than one-fifth of sales of standalone streaming devices in the last three months of 2013.