The young Lions travel to Bucharest to face Romania U21s at 7pm in the UEFA Under-21 Championship Group G qualifiers on Friday, September 3.
England will then welcome Kosovo U21s to Stadium mk for Tuesday, September 7th's 7pm kick-off.
Aarons has made 11 appearances for the England U21s side so far.
Williams, who has been placed on standby, could be called up to the squad up until Monday, September 6.
The Manchester United loanee has made one appearance for the U21s to date.