You can't blame Roku. They just supply the hardware to watch. It's up to the networks and developers to offer programming and create the channels. When it comes to sports, it is VERY expensive at all levels. I plan on cancelling my regular TV service soon due to the obscene RSN (Regional Sports Network) fee and high costs of carrying sports networks that I don't give a bleep about.
Basically, most sports still have ties with cable/satellite/broadcast services that highly restrict what can air and who can see it. You need to carefully research any subscriptions before paying any money. That $99 you spent was probably for the annual plan.
Also, NEVER subscribe through a 3rd party like Roku. ALWAYS go to the service's WEB SITE and subscribe there, after carefully reviewing what is actually available and if it's what you want.