Just ran into the same issue. What worked for me was this:
1) Installing the capistrano-rvm gem and adding
require 'capistrano/rvm'
to the Capfile.
2) Adding my deployment user to the rvm group on the server:
# usermod deploy -a -G rvm
3) Creating two directories in my deployment user’s home folder: .rvm and .rvm/bin
4) Adding this line to my deploy.rb file:
set :default_env, { rvm_bin_path: '~/.rvm/bin' }
Phew! That took a few hours.