If your tomato plants have died due to frost then they're dead and will not come back after frost.
To keep tomato plants alive you need to protect them during frost and if the tomato plants are in pots you should bring the tomato plants inside the house where it's warm during a time when frost is forecast.
If the frost was only a brief frost then you may get lucky and be able to save the tomato plant but if it was a hard frost then sadly the tomato plants are dead and will not come back.
So it's very important to protect the tomato plants during or before a frost to keep them alive.