Use audit logs. The bot will need permissions though:
client.on("roleDelete", async role => {
let member;
try {
const log = await role.guild.fetchAuditLogs({
type: "ROLE_DELETE"
})
member = role.guild.members.resolve(log.entries.first().executor)
} catch (err) {
console.log(err) // simply for debugging
}
if (!member) member = null
})
And now when you access member, it will show null if it couldn't find the executor, but will show the GuildMember who deleted the role if they were found.