Roy's Peak is located just outside of the town of Wanaka. It's accessed from a carpark just off the main road and is popular with hardcore hikers and curious tourists alike. In summer, get there early as parking can be hard to come by. The whole 16km takes between 5 and 7 hours, depending on how often you stop for photos (or to catch your breath as it's ever such a steep trail!)
The track is well-formed and for the more adventurous, there are shortcuts which have been etched into the mountain face. I did the hike in winter so there was snow and the normal path was slippery in parts so I can't imagine what the steeper 'unofficial' tracks are like.
As with any alpine environment, the weather is unpredictable and can change at a moment's notice. Or even without any notice at all. I ascended in beautiful sunshine with blue skies. Not long after having my photo taken at the 'Instagram hotspot' on the lookout, the cloud had come in and visibility almost dropped to zero.
Being such a popular route, there is an honesty box at the start asking for a $2 donation which goes towards maintenance and upkeep of the trail. Make sure you have a gold coin handy when embarking on your Roy's Peak adventure.