In a classical style, melodies are usually divided into 8 bars (4+4) or 16 bars (8 + 8, that also divides into 4+4) and has one of these forms AA' or AB, (you made AA)
If you chose AA' that means that you have to end on the fifth grade (or at least, not in the first note of the scale) in bar 4 and end on first grade on bar 8.
For example:
Ypu did I + IV + I + IV, I IV I V (the laast note was g over a D chord)
If you want a harmonicaly simple theme (as in mozart k310) i would have done:
I IV I (V/V) V, I V(ii) V7 I
I don't have much time more to look your rondo but i think this might help you.
Also, sorry for my bad english, i'm not used to explaining Musical concepts in english.
By the way: try to avoid III - I (bar 11) and II - I (bar 11-12) those progressions are 'weak' maybe you could make III (2 inversion) V; or II (first inversion) V I (or VI)