By TransformationMatrix. Question is where would you like to have the rotation center. If it should be in the center of the [MeterGreetingText] meter, add the followings:
An Angle=XX variable to the [Variables] section. As you probably figured out, this will be the rotation angle. Note that a positive value means anticlockwise rotation, while negative values clockwise rotation.
A TransformationMatrix=(Cos(Rad(#Angle#)));(-Sin(Rad(#Angle#)));(Sin(Rad(#Angle#)));(Cos(Rad(#Angle#)));((([#CURRENTSECTION#:X]+[#CURRENTSECTION#:W]/2)*(1-Cos(Rad(#Angle#))))-(([#CURRENTSECTION#:Y]+[#CURRENTSECTION#:H]/2)*Sin(Rad(#Angle#))));((([#CURRENTSECTION#:X]+[#CURRENTSECTION#:W]/2)*(1+Sin(Rad(#Angle#))))-(([#CURRENTSECTION#:Y]+[#CURRENTSECTION#:H]/2)*Cos(Rad(#Angle#)))) option to the meter you'd like to rotate (in this case [MeterGreetingText] probably).