I lost my Roku Remote, is Roku stick the same as a fire stick where you can use your phone as a Remo

To add to what Emissary35 wrote, there are probably several apps that can act as Roku remotes, but you can find the official one from here:

Roku Mobile App - Free for iOS® or Android™ | Roku

I also have to emphasize what was said about the phone and Roku already being connected to the same network.  You can't use the app to initially set up a Roku device or change its Wi-Fi connection if it's not connected, so you may want to pick up a Roku Voice Remote if you can't find yours to have "just in case".