I agree with Sabir that just upgrading a plane won't cover a generation gap.
The ROSE upgrade will improve the strike ability of the Mirage. After ROSE Stage 3 upgrade the Mirage would have night operation, low level stirke and precision strike capability.
ROSE stage 1 upgrade will give Mirage new
HUD,
HOTS,
INS,
MFD, GPS,EW suite with new counter-measure despensing system for flares and chaff, RWR and a new fire control radar which will enable jet to fire BVR missiles.
ROSE stage 2 upgrade will give Mirage a new and better fire control radar and IRST system for low level operations.
ROSE stage 3 upgrade will give Mirage new avionic suite to enable precision strike capability.