Is predefined page size necessary with roll paper when printing

[nanjeca]

Hi I am using a Epson 7880 on a Windows 7 64 bit PC with Lightroom 3.4.1 and Photoshop CS5 and NO RIP.
 
As I currently operate, I install the roll paper. Next, I define a page size in the user defined section of the printer driver panel. Now, I can organize my page layout within that page and use Lightroom (my prime print interface) to optimize that layout. In other words, I put in a 24" x 39' roll of paper. Then I define a page size of 24" x 33", and then i play within that page.
 
Is this pre-defined page the only way to use roll paper? In other words, can I just put the paper on, and tell lightroom that I want 1 - 16x20, 3 - 8x10s, 10-5x7s, etc, and have lightroom simply use as much of the roll as it needs, and cut the paper whereever it finishes printing? This would optimize the paper much better than me pre-defining a page size and then wasting whatever lightroom doesn't need. Again, by way of example, if I predefine it as 24x33, and only print 2 - 8x10s, I'm wasting a lot of paper due to the predefined page.
 
I hope this question makes sense.
 
Help
 
Mike

[NikoJorj]

Is this pre-defined page the only way to use roll paper? In other words, can I just put the paper on, and tell lightroom that I want 1 - 16x20, 3 - 8x10s, 10-5x7s, etc, and have lightroom simply use as much of the roll as it needs, and cut the paper whereever it finishes printing?

This would be very handy, and, in a word, logical.
But alas, the human species is not that rational, and this valley of tears ain't no perfect world either, and moreover our cameras still show us a jpeg histogram when shooting raw... 

I've hoped that any printer with roll paper handling could do that from the standard driver for long, but no one does AFAIK.
The use of a RIP might solve the problem.

[Schewe]

As I indicated in the Lightroom forums on Adobe, Nope...that not the way print drivers work...you will need to specify a page size to print to.