those roots may or may not be from the current bushes...cutting them and removing them is a pain in the tush - can't do much else tho if you want to
plant stuff!! i've got the same problem and i just keep removing sections of root as i go along.
if you want or need to redo all the soil in one shot, then do so. what i've done is amended a spot when i was going to
plant something.
i also use the licorice root mulch - it breaks down over time nicely and each
spring, i turn over the top layer and work it into the soil and then put down a new layer of it. so, i've basically amended all the beds...just in a lazier way
the type of mulch you have now doesn't break down too well, i don't think...and as longy said, doesn't look as nice as some others...altho, if you like it, then continue using it
i chose licorice root because it doesn't wash away and it continues to look nice even after it's been down for a couple weeks...the added benefit is how it gradually breaks down over time and can be worked into the soil base.