This is not a Rogers issue. I believe that Rogers provides all the channels that are available in 4K in Canada and there aren't many. Most "broadcasters" are 1080i, 720P and some are still 480i. Here's an FAQ on the topic.
In order to broadcast any channel in 4k it requires 4k recording when the content were created.
So, It really depends on the content creators and the broadcasters who are managing their servers to broadcast the channels. I think Rogers wouldn't mind to offer all the channels in 4k if that's available.
Part of this also has to do with the current slate of 4K channels available to be carried in Canada but also whether the provider carries it or not.
Rogers currently carries the following: Stingray Festival 4K TSN & TSN 2 4K Sportsnet Ontario & Sportsnet 4K (This is from the Ontario listings, btw. I'm unsure if for east of Ontario & Ottawa that they use the Sportsnet East feed for when there's no 4K content on the channel)
Rogers previously carried two channels before they got removed from the service: Stingray Now 4K & XITE 4K.