If you want Roll20 to automatically add Tasha's content on Roll20, it has to be purchased on Roll20, or in a game created by the purchaser of Tasha's on Roll20 who has decided to turn on sharing for the content. If you don't want to purchase it on Roll20, you can enter anything you like into a character sheet manually. The Roll20 compendium version just allows you to use its content with Roll20 automation.