Adjacent Channel Interference With Different symbol rate than desired signal

I have a question on modeling the impact of adjacent channel interference on the desired signal. Mathlab has many models with adjacent and co-channel interference in the example library. In the examples provided, however, the desired and interfere signal bandwidth are the same. I have a situation where they differ. For my situation, the desired signal has signal bandwidth of 30 MHz, while the interferer has a signal bandwidth of 20 MHz. Both use the square root cosine filter before transmission. I don’t know how to simulate this scenario?