Photo stream photos will display a trash icon on the bottom right of your phone when you tap Select, then tap the photos to select them. The only photo albums on your phone that won't display a trash icon are photos that were originally synced to your phone from a computer using iTunes. Those photos can only be synced off again using iTunes.
If that's how these photos got on your phone and they are no longer on your computer, the only way to transfer them back to your computer is to use a 3rd party app such as PhotoSync. After transferring them to your computer you can delete them by creating an empty folder on your computer, then syncing this folder to your phone by selecting it on the Photos tab of your iTunes sync settings and syncing.
If these photos really are in your my photo stream album and selecting them does not reveal a trash icon, then something is wrong with your phone and I suggest you back it up and restore it.