Add utility method to get a server's role by ID
Add utility method to get a server's role by ID

sarsntony/discordrb,sarsntony/discordrb,VxJasonxV/discordrb,VxJasonxV/discordrb,meew0/discordrb,meew0/discordrb,megumisonoda/discordrb,megumisonoda/discordrb,Roughsketch/discordrb,Roughsketch/discordrb