I am having trouble rolling my fondant big enought cover 12in cake.
Totally wearing out my hands/arms, any ideas for short cuts?

Try sticking it in the microwave for 8-15 seconds on low power- it's easier to roll if it's not rock solid.

tell us more about the size of your cake. If it is 12"x4". you must add the 12" plus double the 4 " hight and you will add these 2 no.(12" plus 8"(doubling the sides) . this is 20" and then a at least 2 more inches. this makes it 22 " you need to roll your fondant. Either roll it out on powdersugar on your counter top(have your cake pre iced (not too thin or too heavy) or roll it out on a slightly greased mat to at least 22". if it is a round cake then try to roll your fondant round . It it is a square cake , try to roll it out square. this helps in the end. If you roll it out on the counter top. then when you go to pick it up to place on cake. pick it up with your rolling pin. just roll the fondant up on the rolling pin and lay on cake. If rolling on the greased mat , then pick up mat and lay over the cake and rub top and then easily pull off the mat. then go from there. Roll your fondant betwen 1/8" to 1/4" thick, especially if you are new to this. Also look on youtube, there are plenty on there showing how. Also look at sweetwise showing "the mat" and how good she rolls fondant . Planet cake is another one showing how and so many more. Also satin ice has some great tutorial on all of this hth

Stand on a stool if you're rolling (or kneading) on the counter, then your body does the work and not your arms/wrists- Sharon Zambito's excellent tip! Also, would recommend her video for Flawless fondant. And I would invest in a really good silicone rolling pin, if you haven't already. I have a handle-less one and would buy one with handles next time..

I do what genevieveyum and cakesrock suggested. I heat for less than 10 seconds (make a huge difference) and I stand on a stool using a silicone pin to roll it. I'm only 5' tall. Makes all the difference in the world.