We just bought our house in Waves and went through all of the info we could find on Spectrum. They told us that we needed to have at least one cable box on our account to use the streaming service. So, we put that box in the main living area and put a Roku Express ($25 each, one time cost) in each of the five bedrooms. Much cheaper than monthly rental fees per box. Roku does come with the Spectrum app and last weekend I tested all five streaming at once on different channels with no problems. You do need to be on the Spectrum WIFI to use the app.
If you get Roku, you will need to sign up for one of their accounts. If you have renters, like we do, make sure that you use the option to not sumbit a credit card. There are some services on Roku that cost extra fees, but with not credit card on file they can't be used.