It is certainly OK to use something other than candles in a ritual if you can't have open flames in your room. One thing would be to use the battery-operated candles you can find at any hobby store. They will give you the ambiance of candlelight without the flame.
Secondly, think about what it is that candles signify. Are they just there for the light they give? In that case you can get the same effect by simply dimming the amount of light in your room.
Are they there to represent the God and Goddess? If that is what they are doing you can choose something else to do the same thing. Statues come to mind. Or you can work more symbolically using for instance a shell to represent the Goddess, or a cup of water.
Candles, like any other tool, are great. But if you can't use them there are any number of ways to substitute something else.