The Roku app can only be used for a Roku that is already connected to the local network, and to set that up that you'll need a remote. The 2500 is pretty old, having been released in 2012, but Roku has not changed its set of infrared control codes since then. Any inexpensive universal IR remote you find at the dollar store or Walmart will work, as long as it lists that it supports Roku.
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Roku Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X | Roku Streaming Stick 3600
