I have them saved on my MacBook in iPhoto in my library.
How did you import them into your iPhoto Library on your Mac?
Did you connect the phone and download them? Or do you just see them in the PhotoStream on your Mac? If they are only in the Photo Stream, you still need to import them. But if you see them in an event in your iPhoto Library on your mac, they have been properly imported and are save.
But anyway, to be really sure, that you will not risk losing your photos, create a current backup of your iPhoto library, before you start deleting photos anywere.
And do you backup your iPhone regularly when syncing it? The backup will contain the contents of your camera roll.