Juniper re potting

[Kyriakos]

Hey guys just looking for some advise for my juniper

I have only had this plant for about a week and I’ve noticed under the moss the plants roots are fairly exposed and situated high in the pot

I bought the plant for bunnings and there is also a fair amount of pebbles 2-3 cm from the top until the soil

Should I look at adding soil and removing rocks or repotting lower into the pot

[shibui]

The mass produced bonsai usually have pebbles glued on top of the soil to help hold it all together until it is sold. We usually encourage people to remove those glued on stones so you can better monitor soil moisture.
The exposed roots won't hurt the tree. Some of the smaller ones might die as they dry out but losing a few small roots will not compromise the tree as long as there is still plenty deeper in the soil. If there was some moss to retain moisture these may even be new roots that have grown closer to the surface.
Covering the roots will protect them and usually allows the roots to grow better and thicken faster. Burying the roots can be achieved simply by adding some more suitable potting mix over the top. Mounded soil will tend to slowly (sometimes quickly if you water aggressively) wash away again.
Repotting the tree lower in the pot is another option.
In bonsai there is often no one right answer. A lot of what we do is dictated by what we think looks good so it is really up to you as to which path to take here.
Assuming you are somewhere in Australia it is a good time to repot junipers now if you decide to try that solution.

Adding a location to your profile will allow far better advice for your local conditions because even Australia is a very diverse place.