There is nothing for Roku except the official NFL channel - and it's a pay channel. I can think of nothing free, unless you use PlayOn's "PlayMark" feature. Assuming you own a PlayOn. It's currently $20, It requires you to run the playon server on a computer on your network. However, if you have a computer or tablet that you can connect to your TV, you can stream from one of those devices. http://www.nfl.com/superbowl/49/live/watch-free-live-stream-online
There is also a chance you could improve your antenna setup before the game. Let us know if we can help.
I checked around, and didn't find any mention of the game being available on a Roku channel. I would try the official NFL channel, NFL Now!You might try Nowhere TV, FilmOn, channel PEAR, Nowhere Stream. All are private channels. Also, Livestream and NBC News, but those are longshots.
I should remind people about what happens when a major sporting event is streamed: Server crashes, freezing, degraded picture quality, all due to the large number of people trying to watch at once. You may be better off trying to improve your antenna system rather than attempting to watch online.
More specifically: channel PEAR is powerful API that acts as a media library in the cloud for users to add to and access with various devices. You can compare it to Plex/XBMC without the ability to transcode, and without the need to be running 24/7 locally. No actual media content is hosted on channel PEAR.