Merge Rows into one row parsing two columns

 - Group by SYSTEM and USER

 - Aggregate into a List of Roles

 - Expand the list into new columns

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WKq4sNlTSUSotLgJRRfk5qQqGSrE6WCWMcEkY45IwwSVhikvCDE3CCMNVRqg6gOKxAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [SYSTEM = _t, USER = _t, ROLE = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"SYSTEM", type text}, {"USER", type text}, {"ROLE", type text}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"SYSTEM", "USER"}, {
        {"Role Count", each Table.RowCount(_)},
        {"ROLE", each [ROLE]}}),
    
    #"Number of Roles" = List.Max(#"Grouped Rows"[Role Count]),
    #"Removed Columns" = Table.RemoveColumns(#"Grouped Rows",{"Role Count"}),
    #"Extracted Values" = Table.TransformColumns(#"Removed Columns", 
        {"ROLE", each Text.Combine(List.Transform(_, Text.From), ";"), type text}),
   
    #"Split Column by Delimiter" = Table.SplitColumn(#"Extracted Values", "ROLE", 
        Splitter.SplitTextByDelimiter(";", QuoteStyle.Csv), #"Number of Roles")
in
    #"Split Column by Delimiter"