The only1 instrument that directly indicates the bank angle is the attitude indicator, also (especially formerly) known as the "artificial horizon". As another answer has noted, many other instruments give indirect indications of bank angle, and by using them appropriately, it is quite possible to keep the wings level even with no direct indication of the ...
Many instruments can indicate roll. Here is a list in order of Primacy according to the Primary-Secondary Method of Instrument Flying:
Rate of Turn Indicator (when TC is absent)
Inclinometer (actually only measures coordination)
In the Control-Performance Method of Instrument Flying, and what most ...