As you say, using that amount did totally dominate the taste.
Luckily we were trying for a really dark, 'roasty' stout for winter, and it came out better than i could have ever expected! Very creamy, and and a little harsh at first, but after a month in bottles it went down very well.
I certainly wouldn't use that much roasted barley in any other recipe.
I had thought crystal malt would do the job, I just have no idea of how much to use!
I've seen some amazingly 'red' red ales in my time, but i've never been able to pin down what exactly it is that can achieve that colour.