Even though you eat and do make kiddush on the roof-top, where the moonlight illuminates the table, nonetheless you have to light the shabbat candle and say a bracha over it, because although the pshat rationale of lightning the shabbat candle is “shlom bayit”, peace at home, there is an (additional) obligation because of the sod, the secret. Thus, I noted in my holy book “Mikavtze’el”, and look as well in the “Eshel-Avraham”, Ch. 263, small paragraph 21; look there.