I believe you're a:
I'm the everyday millipede, come look at my feet!
A toothbrush has many, many bristles, just as a millipede has many, many feet.
I put a smile on your face with my frothing stampede.
Brushing your teeth with a toothbrush and toothpaste causes the paste to froth and makes that smile white and new!
I walk inside you, walk in circles and in lines,
This describes good brushing action, with back-and-forth ('lines') and circular motions in your mouth ('inside you').
My legs can be straight or angled, arranged in different designs.
Modern toothbrushes come in so many different designs, ranging from the standard straight-bristled look to designs specifically for targeting particular parts of the mouth and cleaning hard-to-reach places with angled bristles.
I trample rosy flesh and hardest bones,
The toothbrush's bristles (feet) walk on your gums (rosy flesh) and teeth (bones).
Yet in every household you'll find my clones.
Pretty much everybody has one!