Thank you for the inquiry regarding using multiple Roku at the same time. We have profiled your internet connection between our service site and learned that it might not be fast enough to handle 3 concurrent session at the same time.
If you like, we can set up test accounts for you to test for a period of time, and this will help determine whether it's workable or not.
As much we like to support multiple con-current devices, current internet infrastructure prevents us to do so. Mainly because connection speed cannot be guaranteed (from both yours or our connection), and the cost is not yet reasonable.
thank you for your support - please let us know how we can help further on.