Yes you may watch your rented movies on other platforms for as long as you log in with the same account you used to rent it. 

 

Via Roku

a. Your rented movie on the website will be displayed under the "Purchased" section

b. Choose the movie title that you have rented

c. Choose Watch to play the movie

 

Via Android or iOS

a. Tap Movies found at the bottom of the screen

b. Choose the movie title that you have rented

c. Tap Watch to play the movie

 

Via Samsung Smart TV

a. On the homepage, go to Movies For Rent

b. Choose the movie title that you have rented

c. Choose Watch to play the movie