Usually Developer’s Responsibilities comes under SRS. Following things you can write in Developer’s Responsibilities:

• Developer shall develop custom software which will modify, customize, amend, enhance or otherwise change the following pre-existing Developer’s software packages to fulfill the requirements of Company.
• The requirements to be fulfilled by the custom programming to the above listed packages which are presently undefined. The defining of Company requirements shall occur in phases by phase, each phase shall be designed, approved, programmed, delivered, tested, and accepted pursuant to the procedures listed below.
• The developer is responsible for (a) developing the system, (b) installing the software on the client’s hardware, (c) conducting any user training that might be needed for using the system, and (d) maintaining the system for a period of one year after installation.
• Gather and evaluate user feedback
• Produce clean, efficient code based on specifications
• Integrate software components and third-party programs
• Verify and deploy programs and systems
• Troubleshoot, debug and upgrade existing software
• Recommend and execute improvements
• Create technical documentation for reference and reporting