The Pembroke College website says "we also do our best to offer college accommodation to all graduate students new in Oxford", so they'll give you a room for your first year but afterwards you'll have to find somewhere else (this is fairly standard for Oxford colleges, there might be some that can offer rooms to second-year graduates (St. John's??) but this is uncommon). Many students living out live in Iffley, Cowley, Headington or Jericho areas. You can see where Pembroke has rooms for first-year graduates here - some are on-site, some aren't, it's not possible to say where you'll be at this point.