Y'all are posting in English. That's a problem. Corporations only understand Money. Our posts here sound like adults in a Charlie Brown cartoon to them. Here are a couple things you can do that Comcast will understand:
Cancel your TV subscription. I just did this myself. Comcast is betting you won't do this because of their stranglehold on the content (not only HBO) that you want to watch. OTH, after using Roku for a few months, I found that I only watched Comcast TV for an hour or two a week -- definitely not getting $20~40 per hour of entertainment from Comcast TV.
Get Comcast's easements revoked in your area. Working on this myself. This is both harder and easier than it sounds, but it's worth investigating -- especially if Comcast has a monopoly in your area, like it does in mine. Even something as small as writing an email to your town council can help.
Convince streamer manufacturers to pressure HBO, perhaps even to the point of naming HBO in their lawsuits against Comcast. HBO is FAR from innocent. There is no need for them to assist Comcast in blocking Roku, yet they are doing just that. That proves collusion and makes HBO equally guilty. This problem would vanish if HBO refused help cable providers block Roku.