For this great fare you would have to accept one additional layover during your travelling on the other hand you may reach Sri Lanka during main tourist season for really attractive fare. In case of interest please look for travel dates between 8th of April and 11th of June 2015. (based on date of your outbound flight to Sri Lanka).
Accommodation - compare hotel rooms in Sri lanka already from €11.
Booking samples
Italy - Colombo - Germany for €203
Italy - Colombo - Vienna for €248
Italy - Colombo - Zurich/Paris from €323
Italy - Colombo - London for Ł288
Travel date samples (based on routing Rome - Colombo - Frankfurt)
9. - 20.4.
16. - 27.4.
24.4. - 5.5.
7. - 21.5.
11. - 28.5.
18.5. - 4.6.
27.5. - 15.6.
8. - 18.6.
Plenty of low-cost airlines are connecting Rome with main airports in Germany or other European airports. We recommend to use service of Skyscanner to quickly find out which low-cost airline offers the most competitive fare.
Booking sample of cheap open-jaw flights to Sri Lanka from Europe for €203 here. In this case you would be departing from Rome to Colombo on 9th of April. Your return flight from Sri Lanka back to Frankfurt would take place on 20th of April 2015.