Sqlserver union and join operation

I have two coloumns in a two table say name and emailid  in table x and regname and mailid in table y . I want to unite column name and reg name into a column and emailid and mailid into another column as table c. I also want Rollno of table y into  table c.How I can do?

I was able to unite name and regname into column name of table c and mailid and emailid as coloumn mail in table c but not able to attach rollno in tablec in a single sql expression.

To unite columns into name and mail I used union expression but how to attach roll no also.