Like many cable-type channels Bravo only makes its programming available to those paying for it as part of a paid subscription to a service that carries the channel. That service doesn't have to be a bloated cable or satellite service however. There are several you can subscribe to and run on a Roku. Ones I think carry Bravo are Fubo TV, ATT Now, Sling Tv, and YouTube Tv -- there may be others.
Savings in cord cutting usually come from picking and choosing which of the lesser offerings you wish to pay for instead of paying for cable or satellite services bloated with channels you mostly never watch.