If you're in a location where you can pick up your local broadcast stations by antenna, you can watch these directly for free by connecting the antenna to the coaxial antenna input on your television. If you can't do this, you'll need a tv provider of some sort to bring these stations to you.
Aside from local broadcast stations, cable-type channels want to be paid. When you have a paid subscription to a "tv provider" service that carries these channels (like your DirecTV subscription), they receive their pay out of the subscription fees you pay that provider. When you don't have a subscription to such a provider you are not paying for those channels.
Many cable-type channels make their content available for streaming via a "TV Everywhere" channel app for those paying for the channel through a provider as mentioned above. There are several services you can subscribe to and run on a Roku that may carry the channels you are interested in at a lower cost than you are paying now. Ones that come to mind to check out for any particular channel would include:
• Hulu plus Live TV • Sling • philo • Directv Stream (the new name for the former AT&T TV) • YouTube TV (which is currently accessed through the ordinary YouTube app on Roku) • frndly • fubu • vidgo ... there may be others.
In addition there are many free streaming channels that do not require "tv provider" accounts. Most (all?) of them are supported by unskippable ads.
There are others you can subscribe to which have free or lower cost tiers with ads but also have higher cost tiers with limited or no ads.
There are several places on the net where you can look up which streaming providers carry a particular channel of interest. Here are several such pages:
Savings in cord cutting usually come from picking and choosing which of the offerings you wish to pay for instead of paying for full blown cable or satellite services with scores of channels you never watch.
Roku Community Streaming Expert I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well. If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
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Let me add one thing to what @makaiguy said. If you don't have to watch network TV channels (ABC, Fox, NBC) live, many programs that air on those are available hours after airing via Hulu standard service, $6 (soon $7)/month. CBS is available live for $10/month via Paramount+. For standard cable channels, several of those services listed by @makaiguy include the four major network affiliates.
DBDukes Roku Community Streaming Expert Note: I am not a Roku employee.
If this post solves your problem please help others find this answer and click "Accept as Solution."