Can i use self raising flour instead of plan flour in a basic white sauce?
No, because self-rising flour is flour with salt and baking powder (the 'rising' part) already incorporated into it. Not the thing for a bechamel.
No. Use plain all-purpose flour, or Wondra if you can find it. Self-rising flour contains baking powder and it'll give your sauce a funky flavor.
Actually, it's been my experience you CAN use it if you're going to be flavoring the white sauce -- say with cheese, or a generous portion of spices or peppers. But I agree, a/p is much preferable. I don't even keep self-rising flour on hand any more.
Agree with all the others, self-rising can't be substituted for AP in non-baking applications, and also with KayB that I don't keep it around any longer, since so few modern recipes call for it. Self-rising can be very easily substituted with AP flour, baking powder and salt. Ratio is for 1C self-rising, use 1C AP, 1/2 teaspoon baking powder and 1/2 teaspoon salt (salt in addition to what's called for in your base recipe).