Hello, I’m Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority.
Sorry to hear you’re having trouble.
The roku is really a separate function/device from directv.
Can you tell me the model of the tv and which roku device you have?
Thank you for confirming.
You cannot do much with your current set of equipment.
If you had a wifi booster or repeater, you could use that to increase the wifi from the marina and connect the roku to that.
The antenna you have (presumably just a high range usb based wifi adapter) for the computer won't benefit the roku in any way here.
IF your roku (not positive exactly which model you have) has an ethernet port, it might be possible to bridge (share) the connection off your computer to the roku.
Otherwise, you'd be better served by getting a wifi booster instead: http://amzn.to/29qnZ5m
Do you need more help with this, Jackie?