Hi ,my name is Jack
Would just like some details here before committing to this question;
Although your question is in the recorder and players category ,from what I gather you are saying that the picture is too large for the screen and the captions go below it , is that correct ?
If so then we would be talking about a tv ??
O.k then a few questions ;
What is the model number of the tv ?
Which version of Roku do you have ?
Is there a cable box or satellite receiver connected to this tv ?