Rolling Roof Purlins is not "Optional", and there is no such thing as a "seamless application" as one company in Jacksonville is trying to sell it. If someone has told you otherwise, they are either lazy and in too much of a hurry to do a proper job, or so unskilled that they don't know what is required or why. Not rolling roof purlins poses a threat to the structure itself. Do not hire anyone that does not roll the purlins every time, not just because you ask them to. The odds are, it won't get done.
I have attached a letter from the Engineer at Aluminum Screen Design, explaining the necessity of rolling the roof purlins, and that if an installer is not going to do so, that the job must be re-engineered to take the additional load. I would also like to point out, that a company which is operating without a contractors license, but that can still legally perform rescreens, can not legally have a job re-engineered. Do not throw your money away by going with another company.
Not rolling the roof purlins takes about half of the time to install, and lasts about half as long as individually rolled panels.