Here are the sentences changed into the passive voice:

1. The road is going to be mended by them.
2. Cigarettes are not going to be smoked by her.
3. The uniform must be worn by you.
4. Delicious meals can be cooked by him.
5. I will be phoned by my parents tonight.
6. A coconut tree is being planted by them.
7. An essay has just been written by me.
8. He is not helped by us; it is done by him himself.
9. A dog was hit by my roommate yesterday.
10. My girlfriend had been met by Jack.
11. English songs can be sung by her.
12. This exercise must be finished by you before you go to bed.
13. The environment should be taken care of by us.
14. She will be informed about the schedule by them.
15. I won’t be visited by him next month.