Try load xls file and get this error. There is console log:
irb(main):001:0> require \'roo\' => true irb(main):002:0> a = Roo::Excel.new(\'/home/a.xls\'
Try to fix version of "spreadsheet" gem to "0.9.0".
In my case adding
gem "spreadsheet", "0.9.0"
right before roo gem made a trick.