Simple recipe - 'kambing guling'

I like cooking but I don't like the idea of spending long hours in the kitchen.
This is one simplified recipe of what I almost always do - simplified kambing guling -.
I and Pasko really like lamb. I like to cook tongseng, gule, krengsengan, nasi goreng kambing.
One day after cooking a roast lamb with honey & lemon sauce, I was inspired to cook kambing guling in similar way of the roast lamb thing.

I found that it tastes yummy and we are happy with it.
(it only requires 10 minutes preparation and 90 mins cooking time... long hours still, but I only need to spend 10 mins in the kitchen plus wash 1 knife, 1 chopboard and 1 bowl!)

Here is the recipe:
1 kg roast lamb

Spices:
75 g ground coriander
1 teasp white pepper (finely ground)
1/2 teasp ground nutmeg
about 5 garlic, finely chopped
1/2 tablesp salt
1/4 palm sugar (about 25 g)
enough kecap inggris (worcestershire sauce)- about 30-40 ml
1 tablesp vegetable oil
plenty sweet soya sauce, about 50-75 ml

Preheat the oven to 200 degree (C).
Mix all the spices in a bowl, and put in the roast lamb until it's covered by the spices.
Put in the oven bag (medium size). Follow the instruction of the use of the oven bag (tie it and cut about three small holes on its top.
Put roast lamb into the oven for about one hours.
It's ready to eat. However, if you like to have more "kambing guling alike":
Carefully tear the bag and separate the lamb and the juice. Cut the lamb in big slices and put in the oven rack, and cook it for another 20 mins or until you think it's enough (it's really up to you...)
Another option to make it brownie and really like kambing guling, move it to the griller, and grill it about 5-10 mins in medium.

Good luck!