There's only 1 true west indian roti shop in the downtown core called Coconut Grove on Dundas Street between University and Bay Street (183 Dundas Street West) just west of Chestnut. You get the west indian styled roti here (Trini & Guyanese style). You should prob call them ahead and ask them to prep the "Paratha Roti or Buss Up SHut Roti" ahead of time.
I second Eastern Twist. Metro(Dominion) has 3-4 varieties of frozen parathas. King Palace on Church sreet has Paratha on its menu but I never tried it. Also Curry in a hurry at Bloor and Landsdowne has a paratha rotti - which is a Sri Lankan spin on Paratha.
820 Church St, Toronto, ON M4W2M9, CA
I have no idea what a buss up shot is (sounds good though), but Eastern Twist on St. Clair, at Bathurst makes delicious Indian/Middle Eastern wraps that are wrapped in paratha. Delish. Not really downtown, more midtown, but not far and subway accessible (St. Clair West station).
Ali's in Parkdale serves Paratha Roti/Buss-up-Shut. Not quite downtown, but at least it's closer to downtown.
check out this vintage chow thread on the topic: http://chowhound.chow.com/topics/99014
Ali's West Indian Roti Shop
1446 Queen St W, Toronto, ON M6K1M2, CA
If this is the Parantha as in the Indian thick bread fried in oil, often stuffed with potatoes, then you can find it at most of the indian restaurants.
The Buss-Up-Shut is the same thing, though its often simply fried and not stuffed.
the Indian Parantha is also found pre-made at indian grocery stores