If you are a local, you would know Tai Hing Roast Kitchen (太興燒味). The restaurant is famous for the dishes of Cantonese food barbeque pork （叉燒） and roast pork (燒肉). It has about 40 branches across Hong Kong so it will not be hard for you to find one.
I have not visited the restaurant for quite some time. Recently I visited one and ordered barbecue pork and roast pork for lunch.
With drink, the set lunch costs HK$54, which I think is expensive. All prices have gone up in Hong Kong anyway. The last time I visited Tai Hing, it costed about HK$30 for a plate of rice with roast meat. What a price now.
However, if you want to have a taste of Cantonese style roast meat, visiting Tai Hing would be an easy way to satisfy your wish. The bbq pork is not outstanding, but the roast pork is worth trying for its crispy roast skin.
Check out here for all the branches of Tai Hing Roast Kitchen.