while calling stored proc pass Null
exec [dbo].[RoomDetails_Insertquery] @type=2,@roomno=200,@noofpersons=null,@roomtype='something',
@amt=2000
or in the procedure,
while declare @noopersons set it as default
CREATE PROCEDURE [dbo].[RoomDetails_Insertquery]
(
@type int,
@roomno bigint,
@noofpersons bigint =null,
@roomtype nvarchar(150),
@amt bigint
)
and you can pass only the other 4 parameters