Conclusions:
I. Some Flats are Buildings.
II. Some Apartments are Flats.
III. No Building is a Roof. Statements:

From Statement I. No Building is a Flat (E) → Conversion → Some Flats are not Buildings (O). Hence conclusion I does not follow. No Building is a Flat (E) → Conversion → No Flat is a Building (E) + Some Buildings are Apartments (I) → Some Apartments are Flats (O*). Hence conclusion II does not follow. No Building is a Flat (E) + Some Flats are Roofs (I) → Some Roofs are not Buildings (O). Hence conclusion III does not follow. From Statement II. Some Buildings are not Flats (O) → Conversion → No conclusion. Hence conclusion I does not follow. Some Buildings are Apartments (I) → Conversion → Some Apartments are Buildings (I) + Some Buildings are not Flats (O) → No conclusion. Hence conclusion II does not follow. Some Buildings are not Flats (O) + All Flats are Roofs (A) → No conclusion. Hence conclusion III does not follow. From Statement III. Some Buildings are Flats (I) → Conversion → Some Flats are Buildings (I) . Hence conclusion I follows. Some Buildings are Flats (I) → Conversion → Some Flats are Buildings (I) + No Building is a Apartment (E) → Some Flats are not Apartments (O). Hence conclusion II does not follow. Some Buildings are Flats (I) + All Flats are Roofs (A) → Some Buildings are Roofs (I). Hence conclusion III does not follow. From Statement IV. All Buildings are Flats (A) → Conversion → Some Flats are Buildings (I) . Hence conclusion I follows. Some Buildings are Apartments (I) → Conversion → Some Apartments are Buildings (I) + All Buildings are Flats (A) → Some Apartments are Flats (I). Hence conclusion II follows. All Buildings are Flats (A) + No Flat is a Roof (E) → No Building is a Roof (E). Hence conclusion III follows.