In the name of Allah the most beneficent and Merciful
Working in an environment which is based on Riba (Interest) is not permissible if the employment entails involvement with Riba.The Hadith of the Messenger of Allah clarifies four types of people who are cursed;The Messenger of Allah (May Allah bless him & give him peace) invoked curse (la`na) on the receiver of interest, the payer of interest, the scribe and the two witnesses, and he said: “They are the same” (i.e. in sin). (Sahih Muslim)
Therefore the following employments in a bank would not be permissible
1. Bank Manager
2. Mortgage advisor or advising customers or interest
The following would be allowed,
Call centre assistant who advises customer of their transactions or takes complaints etc.
Technical assistant who is a Computer specialist or assistant
Cleaner, doorman, security etc.
Basically any role that does not have an involvement is dealing with Riba is allowed, otherwise not.
Of course Allah knows best.