How to view certificates from my keychain on iOS?
You can find certificates installed on your device in Settings → General → About → Certificate Trust Settings. Here you can switch root certificates on and off as you please.

                                         

As shown by the small words in the screenshot, certificates enforced by a profile can't be modified here. Profiles are installed in Settings → General → Profiles. You can't turn such certificates on/off — instead you have to uninstall and reinstall the profile.