Hi @vipinmann,
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
Unfortunately, due to the wind loads that a shade sail will apply to its fixing points, it is not a simple case of attaching it to the fence and the roof and we do not sell a kit for this purpose.
On the fence side of the gap, you would need to install posts, like these Australian Handyman Supplies 89 x 89mm (90 x 90) x 3.0m Galvanised Steel Fence Posts, in a similar fashion to what is shown in How To Install a Shade Sail, with a 5-degree angle away from the house.
If you were to attach the shade sail to the alfresco roof, you would need to speak with an engineer to ensure that, firstly, it is capable of supporting the additional load from the shade sail, and that it is mounted to the roof in a way that would transfer the load into the structure, not just the fascia. Unfortunately, when wind loads are involved, you can't really take chances, as they can get surprisingly strong.
If you kept everything separate and installed posts on both sides of the opening, it would be a much simpler task.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
