'We're after the same rainbow's end' means that we have the same goals, hopes and dreams. Idiomatically, to be 'after' something means that you are looking for it. This is based on the popular myth that there is a pot of gold at the end of a rainbow. Cynics, of course, would say that finding the 'rainbow's end' is an unattainable goal. After all, a rainbow is just an optical illusion and it has no physical end. But we can all dream, can't we? 'Waiting round the bend' means that it's just around the next corner. Imagine that you are walking or driving along looking for something. If this thing is 'waiting around the bend' for you, it means that you are very close to your goal but you just can't see it yet. It's a romantic and optimistic image.