I would be concerned about the viability of streaming 1080p video via 2.4GHz, if any of those devices depend on 2.4GHz. 2.4GHz in 1x1 or 2x2 configs will offer less than 100mbit of real world throughput, and in more congested environments, offer even less at range.
Note that small form factor devices like streaming sticks don't have the best wifi antennas on their end, so the infrastructure really has to make up for it. Some of them don't even offer great throughput due to architectural limitations, and even the best wifi network can't make up for it....
I would highly recommend deploying an AP closer to the location where the Roku Streaming Stick is, to see if that could improve performance. If not, honestly, it may be time to look into another streaming system with better wireless performance, like a full-sized Roku box, or a new generation Apple TV with the plex client. Both in my experience have far far better wifi implementations capable of hundreds of mbit like your phone.