Does anyone know why some cake decorators use jelly roll pans for square and rectangle cakes but use regular cake pans for round cakes? It seems like the square and rectangle cakes are torted more this way since the jellyroll pans make very thin layers. Also, what are the baking differences on jellyroll pans?

I'm completely guessing here but I'd say it is because it is much quicker and easier to simply cut a 1 inch high jelly roll cake into squares to stack rather than taking the time and effort to torte cake layers to get a 1 inch layer. It also would be less fuss and muss to prepare and clean up one jelly roll pan as opposed to multiple square pans.

also, on an old cake boss episode i overheard them saying in the kitchen that one sheet (which are baked in the jelly roll pans) only took 28 minutes in there oven- pretty quick if you ask me

Some bakeries even use sheet pans to make round cakes. They take a lot less time in the ovens. In some cake shows you can see how they cut the rounds with the rings and even how they assemble them inside that ring.

Like this, but of course, not with a pan, but with a real pastry ring.

http://www.cakejournal.com/archives/cake-tins

I've done that, with this pastry ring.

http://www.pastrychef.com/ADJUSTABLE-CAKE-RING_p_1185.html

When I did this cake (only the dock is cake) I used 9x15 jelly roll pans. I baked a total of 12 layers, but I only needed 10. When I put it together I stacked the first, third and fifth layers using two 9x15s side by side to make a 15x18. For the second and fourth layer I cut one caike in half, centered the whole one and filled the sides with the two halves. That way I didn't have to tort, the interlocking layers held the whole thing together, and I had a good solid surface to apply buttercream and fondant. If I'd had to tort a single cake that size, I would have made a mess of it for sure.

http://cakecentral.com/gallery/2050053

I've also baked round layers of less than an inch when I want a torted effect without actually doing the work. It's especially useful with larger cakes like this one that used three 14 inch layers each one inch thick:

http://cakecentral.com/gallery/1949660

I also use the jelly roll pans when I'm going for this effect:

http://lamaisondesgateaux.blogspot.com/2010/12/et-maintenant-quelque-chose-differente.html

shanter, if you have a hard time picturing it, here's a blog, scroll down.

http://dimitranas.blogspot.com/search/label/Торти%20празнични%20-%20Feierliche%20Torten%20I

http://dimitranas.blogspot.com/2009/03/skyline-vienna.html

http://www.flickr.com/photos/36641529@N06/5250574019/in/set-72157625574413214

Dimitrana makes all her cakes this way, I think.

And here's another way to do vertical layers, but not with a lot of frosting.

http://iammommy.typepad.com/i_am_baker/2011/02/vertical-layer-cake-tutororial.html

That's amazing! Thanks so much for the info. I may try this.
Shanter

Also, sheet pans store easier/take up less space and are usually kept in higher quantities due to their usage for other things...If one already has dozens of sheet pans, why not use them for as many things as possible including layer cakes, yes?