The sidestick (they don't like it when you call it joystick) is not controlling bank angle, but roll rate in flight. On the ground, the control surfaces are deflected proportionally to sidestick movement in order to perform a check of all surfaces before takeoff.
The details may vary, but this is generally true for all full fly-by-wire Airbuses. From the Airbus A320 FCOM:
When the aircraft is on the ground (in "on ground" mode), the sidestick commands the
aileron and roll spoiler surface deflection. The amount of control surface deflection that
results from a given amount of sidestick deflection depends upon aircraft speed. The pedals
control rudder deflection through a direct mechanical linkage.
When the aircraft is in the "in flight" mode, normal law combines control of the ailerons,
spoilers (except N° 1 spoilers), and rudder (for turn coordination) in the sidestick. While the
system thereby gives the pilot control of the roll and heading, it also limits the roll rate and
bank angle, coordinates the turns, and damps the dutch roll.
The roll rate requested by the pilot during flight is proportional to the sidestick deflection,
with a maximum rate of 15° per second when the sidestick is at the stop.
When the aircraft is in "flare" mode, the lateral control is the same as in "in flight" mode.
(A320 FCOM - Flight Controls - Lateral Control, emphasis mine)
Similar for the A380:
The objective of the lateral ground law is to facilitate aircraft handling on ground.
The lateral ground law is a full authority control law in roll and yaw, with some yaw damping.
However, for small sidestick deflections, the lateral ground law helps the pilot to keep a small bank
angle (less than 2 °), using only the ailerons. In particular, when the sidestick is at neutral, the law will
aim to keep the wings level.
When rudder pedal deflection is close to maximum, yaw damping is removed.
The ground law is gradually phased in during 5 s after touchdown.
Roll Rate Demand
In manual flight, the normal law provides aileron and spoiler control from the sidesticks, to achieve a
roll rate which is proportional to the sidestick deflection, independent of the aircraft speed.
With a full sidestick deflection, the maximum achievable roll rate is 15 °/s.
(A380 FCOM - Flight Controls - Flight Control System - Normal Law)
Regarding your second question:
Regardless of the exact mode you are in during landing (first "in flight", then "flare" then "on ground"), the pilots always have roll control available which will help keeping the aircraft level without the left gear until the speed is too low to do so.