Well, its hard to give hints without giving an exact solution, its really just trial and error.
But for a small (and yes, I mean small) hint just to make sure you start on the right track:
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×After hitting the orb, I moved straight southeast to the bottom before starting to kill the roaches. After that its just a matter of trying out different combinations of stepping/swinging to get the most breathing space.
OK, something slightly more specific..
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×I literally alternated between swinging/stepping as long as possible after the above start.