Could you please list the details of your hardware, everything you think what could be of help, but especially what kind of Amiga you have and where the CD-ROM is connected to and how the jumpers on the drives are set.
Then please give more details about the error. Is there only one requester "Please insert volume AmigaOS3.5 in any drive" or are there two requesters, first "cannot open atapi.device unit 1" and when you cancel this one the other one comes up ?
Generally speaking, you have to make sure that all files needed to access the CD drive are copied to the disk. The installer cannot consider all combinations of hardware, so you might have to tweak it manually. For this you better be a "techie hacker type", but it's not too difficult.
Just load the file EMERGENCY_CD from the Devs/DosDrivers directory of the floppy disk into a text editor. Then check the name next to the "Device =" entry. If it is "atapi.device", then change it to "scsi.device" and save the changes.
If the name is not "atapi.device" then check if a file of that name is in the Devs directory of the disk. If not, copy it from your boot partition. (E.g. if the dos driver says "Device = john.device" then copy "john.device" to Devs).
Bye,
Thomas