I can think of a couple of rather short ones off the top of my head, but nothing more than a few hundred metres long. The one on... Police Road I think it is? That's the biggest I can think of. Then again, I live in the North-East, so perhaps others may be of more assistance
If it's any help, I regularly ride from cnr Warrigal Rd / High St, straight down High St, right at Springvale Rd, left at Waverley Rd and follow to Jells Park. Then turn around and do it in reverse. Not the longest ride, but the hills are pretty decent, especially the first one out of Jells Park... The roads are reasonably wide also and the motorists generally give you a wide berth.