URL Redirection returns only one URL Query string instead of two

Here's my code:
Response.Redirect( !string.IsNullOrEmpty(Request.QueryString["url"]) ? Request.QueryString["url"] : "RoadMap.aspx"); This is the url string which i send to login page after session expire :
http://localhost/BSD/Login.aspx?url=http://localhost/BSD/RoadMap.aspx?Option=1&RPage=D
But when i click login after entering user name and password it redirects like this :
http://localhost/BSD/Login.aspx?Option=1
It does not return RPage query string.