You need 210.25" if you make perfect cuts. If I was ordering it, I would probably buy 215", then I would roll it out and let it sit relaxed for at least 24hours. Then I would make the cuts. BTW, I'm not truly a contractor, but I play like I am somtimes and I once spent a night in a Holiday Inn.
On edit, I see you asked for the measurement to be in feet. Buy 18 feet.
Oops! I forgot to turn the last one sideways. The other guys are correct! 20 feet! Hanging head in shame
Because your last two pieces are wider than the roll you will need more. You will need 82.5" for the first 5 pieces, 92 5/8" for the second 9 pieces, 52.5" for the last two if you turn you sheet 90 degrees to get a full draw width.
You will need a total of 19.21875 or 20 feet to be realistic.