Ok, I know what you're thinking that I'm a weirdo but I love animals and there was something that looked like a ball on top of my shed. I grabbed a broom and sweeped it on to the grass and it was a bird egg. It had been cracked and I think I was responsible. I looked inside and there was like a small amount of yolk fluid and like a white sticky substance.
Usually I'm very strong and I don't care about a lot of things but this whole situation made me feel really bad and I'm upset. Mmmm..
If it had a bird in it there would usually be a small body visible in the egg, most likely the bird has recently hatched or another bird has eaten it... In saying that some birds eggs never hatch. I have a tree on my drive way and often eggs drop from the tree, some smash and leave a small undeveloped bird remaining, others are just empty shells... and you can get eggs which are undamaged but have a repulsive rotten smell and even color which means something has happened during it's time in the egg in which it has died... So I don't think you've killed a baby bird although it's nice to see you care.
You acted to remove what seemed to be a ball from the rooftop. It turned out to be an egg out of the nest. Additionally it may have been cracked hitting the roof. What you describe inside the egg does not sound like a developing embryo, which would have contained at least a little blood. My best guess is that the egg was unfertilized.
Verdict: The fate of this egg was sealed when it hit the roof. You had no hand in killing an unborn chick.
I don't think it had a baby bird in it. I know how you feel though, few months ago I was driving home from work, it was late at night and it had been raining all night. The road was filled with tiny frogs, so many that it was impossible not to run over a few. I was almost crying all the way home.