I've always delt with this by trying to create my items as close to the size I eventually want them at as possible. After I've done my layout.

But.. if you take big rounded text, or circles and scale them down in photoshop often times you get flat squared off edges, instead of smooth rounded edges.

Is there a specific name for this type of reaction, and is there a specific cause, or way to avoid it?

1) pixel averaging 2) not really, but you can fake it by manully adjusting the averaged tones pixel by pixel

build them in illustrator, and scale them as vector before converting to bitmaps.

If you're in PS and resizing a block with rounded corners, set you marquee tool to a specific size, and then snap guides to it. Then just redraw the block, or drag the corner points of the vector shape to fit.

In the end the best practice is simply not to scale them down, a r_d and Napalm point out.