"and if the device malfunctions due to rooting"
good info. as always this will come back to whether Samsung believes (demonstrates?) that the warrantable problem is caused by the rooting. Hardware faults would be very hard to prove of course (screen, buttons, etc), however I'm sure that they would always say that software problems are caused by rooting. So, to my way of thinking, rooting does not "void" the warranty in total - it makes it more likely that Samsung will refuse a warranty claim, particularly for software problems.