So, I had my new components installed yesterday and went for my first big ride today (in between terrible rain storms - no power for 2 1/2 days, much debris in the road). The bike worked just great! It shifted as well as before. There is no rubbing and it is very smooth. I now have 2 new lower gears, and I could get up the big hills much better than before. Instead of 34/27, I have 34/32. Why is there so much lack of knowledge about how to do this from all the professionals? Why would they recommend a mountain bike cassette which is for a 9-speed bike, when a long cage 10 speed derailleur would obviously be more compatible? I think this mismatching of components is why other people have had problems with this conversion.

To summarize, this is what I learned. I installed an IRD 12-32 cassette, with a new chain and a long cage 105 10-speed rear derailleur on my Specialized Ruby Compact. To find out what size derailleur you need on your bike, you need to figure out the chain wrap capacity.

You take the number of teeth on the largest front ring and subtract the number of teeth on the smallest front chain ring. (ex. 50-34=16). It doesn't matter if it is a triple or a compact double. (In a compact double the small ring has the average number of teeth between the small and middle ring of a triple.)

Then you take the number of teeth on the largest ring in the rear cassette and subtract the number of teeth on the smallest ring in the rear cassette. (ex. 32-12=20).

You add these two numbers together to get the chain wrap capacity.
(ex. 16+20=36). The chain wrap capacity for my bike with the new cassette is 36. Then you look up on a website the chain wrap capacity for your derailleur in the bike specifications. My small cage rear derailleur that came with the bike had a capacity of 27 and would not work. The new long cage derailleur has a capacity of 37, so will work with the new larger cassette. An 11-34 rear cassette would probably not work or would need a (larger) mountain bike cassette, but would have the issues of 9 vs. 10 speed.

I hope this will help anyone else who needs to get lower gears on their road bikes. I am really happy with mine.