Is it possible to link my ROKU stick together with a second TV or do I need another stick for that TV?
You need a separate Roku device for each TV. However the Roku devices can be linked to the same account and any app you purchase like Netflix, Hulu, etc... can be used on both TVs.
In addition, you can freely move the stick from one TV to another, but it's not recommended to keep moving it back and forth since something will eventually break.