rest_client didn' work

[kyfahh]

Hi Miguel ,
when i installed rest-client and run the ROCker, always meet the problem :
UNSATISFIED REQUIREMENTS
The building task requires uninstalled gems, please
install them executing:
gem install rest_client

could you please tell me how can i solve it ? Thanks for your help!(ˊᗜˋ)/ᵗᑋᵃᐢᵏ ᵞᵒᵘ*
Best wishs,
krf