I think what they are refering to

ASA hardware can act as a firewall,in other security roles,and in a combination of roles."

They are talking about using the ASA in multi-context mode where obv an ASA device can act as multiple security devices in there own execution space to partition customer traffic.

Hello Sarah,

in addition to the multi context capabilities the ASA has extended capabilities:

it can act as a VPN concentrator

it can act as an IDS

So I think the writer could refer with roles with FW role, IDS role and so on.

see

http://www.cisco.com/en/US/docs/security/asa/asa80/configuration/guide/intro.html#wp1043760

Hope to help

Giuseppe