Bar chart for categorical data count

Your best option is to split the 2nd column at the ", " and create a list, then expand that to new rows. You can then easily create your visual. Here's one way to do it in the query editor.  To see how it works, just create a blank query, open the Advanced Editor and replace the text there with the M code below.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjBMS0s1UNJRCkpNTNFRCC/KLEnVUXAsKCjKL0tVitWJVjJJTEoygSoAC5hVZiRbGAFFoKqgusByBkapaYlpQDmEkGFScpppCqoNSrGxAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [UserID = _t, Roles = _t]),
    #"Added Custom" = Table.AddColumn(Source, "Custom", each Text.Split([Roles], ", ")),
    #"Expanded Custom" = Table.ExpandListColumn(#"Added Custom", "Custom"),
    #"Removed Columns" = Table.RemoveColumns(#"Expanded Custom",{"Roles"})
in
    #"Removed Columns"

Pat