Yes T-Mobile said I get it for three months free but the axing me for a credit card number I do not understand that it is free for three months I would love to try it out but I do not have a car to put on

You would need the Apple TV app on your Roku, not the Apple TV Plus Screeners app. The latter app is for authorised awards voters and authorised members of the press.

Once you have the Apple TV app on your Roku, you should sign in to the app through the in-app Settings (sprockets wheel icon), with your Apple ID account.

When you get a new iPhone (or iPad, iPod touch, Apple TV box, Mac), then Apple offers* 3 months free to new subscribers. The offer has to be redeemed on your new eligible Apple device, in the TV app. Find the “Enjoy 3 Months Free” redeem button there. Once you have the subscription, then the subscription will be available on any of your devices with the Apple TV app, when signed in with the same Apple ID account.

T-Mobile US has an even better offer: one year free with select plans. This offer may or may not be available in other countries or regions where T-Mobile is available.

I am not aware of other offers from T-Mobile for Apple TV+.

Getting a subscription through Apple requires a payment method associated with your Apple ID account (even for a free trial). A credit card would be most convenient. You won’t be billed for this subscriptions during the free trial, but if you stay subscribed then you will be billed monthly (or annually if you prefer) after the trial period.

*Read here how to redeem: Apple TV+ offer - Apple

Read here about the conditions: Apple TV+ offer - Terms and conditions - Apple

Read here if you have trouble redeeming: If you can't redeem your promotion for an Apple subscription - Apple Support