@Dolphin1 The cost of adding ABC, NBC, etc... varies based on your situation. First of all Roku does not sell subscriptions to individual networks. Are you using a Roku TV or a Roku device connected to a TV? If you are using a Roku TV you can connect an antenna and see what local channels you receive. Since Hallmark is a cable channel it will not be available by antenna. The advantage of the antenna is except for the cost of antenna everything is free over the air.
If you are talking about purchasing the channels you have several streaming services that offer all of the channels you mentioned plus many others. Examples are YouTubeTV, Hulu with live TV, Fubo, Directv Stream, and Sling. The price varies from $40/month for Sling with fewer choices to about $75 per month for the others.