Erik,

It's quite possible to identify the wires with just a continuity tester and one trip.

You'll probably need to go get a pencil & paper to follow along...

Starting on the roof, link together any two of the five wires. Now select another two of the remaining three wires and link those together. Identify the remaining open wire as #1, then start your journey down to the basement.

Now, at the other end of the cable, start probing with your continuity tester until you find a pair of wires which complete a circuit. Label these wires #2 and #3 (it doesn't matter which way round; we'll sort that out later). Now find the other pair of wires which gives continuity and label those wires #4 and #5. By default, the remaining wire must be #1.

Thus far, we have #1 identified at both ends and the other four wires identified to the level of two pairs.

Still in the basement, link #1 to #2. Link #3 to #4. We now have all five wires daisy-chained up and down the building. Go get a cup of coffee to fortify yourself for the climb back to the top!

Back on the roof, remove both links you made earlier, but remember which wires were paired by the links. Now, out with the tester again and find which wire has a circuit to #1. Identify this wire as #2. The wire which was previously linked to #2 must, logically, be #3.

Only two to go now. With one probe on #3, find which of the two remaining wires has continuity and label it as #4. The last wire must be #5, of course.

This method has identified the wires and proved that all five have continuity from roof to basement.