In a certain code, 'il be pee' means 'roses are blue', 'silk hee' means 'red flowers' and 'pee mit hee ' means 'flowers are vegetables'. How is 'roses' written in that code?

cannot be determined

IL or BE, so, cannot be determined 

1) il be pee means roses are blue

2) silk hee means red flowers

3) pee mit hee means flowers are vegetables

As, there is no common word for "blue" or "roses", thus we cannot find the code of "Roses"

Thus, the answer stands to be "cannot be determined"