Your post is lacking enough detail to offer any suggestions. What model Roku players (model number, not name)? What firmware versions (saying latest isn't sufficient)? What channels are causing a reboot? How are your Roku players connected to your network, and what sort of TVs are they connected to? While these questions might seem irrelevant, one can never tell unless you have the complete picture.
Dan Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.