Cycling in Sydney Australia
I have been cycling along the now shared pedestrian/bike footpath down from Crown of the Hill Shops. The only things to watch out for are cars exiting the side streets which you should slow down for anyway.
The path along the side of the bridge is not too bad. It is cleaned regularly but a little bumpy from the interlocked concrete panels.
The major obstacle as Tony mentioned is the switchback under the bridge on Roseville side. I second that it is incredibly steep (my Strava gave a grade of 15!) and can be very slippery when strewn with leaf litter and wet. I combat this by staying in my saddle to ensure weight is on my rear tyre but that is difficult to do unless you have strong legs given the steep gradient.
It is then a pretty clear run to Roseville Chase Shops.